assembler training

Assembler Training

Statement Format

Position 1- 8 – NamePosition 9 – BlankPosition 10 -14 – Mnemonic CodePosition 15 – BlankPosition 16 Onwards – Operands Multiple operands can be specified

separated by commas Blank after operand indicates

comment start

Statement Format

Position 72 – Continuation Character Any non-blank character ‘X’ is the most commonly used

character

Position 73 – 80 – Sequence numbers for identification‘*’ in Position 1 indicates a comment line

Statement Format - Examples*********************************************************************** * * * 1. Save callers registers. * * 2. Obtain storage for workarea. * * 3. Initialize acquired storage to X'00'. * * 4. Establish forward and backward chaining. * * 5. Establish addressability. * * * *********************************************************************** SPACE , USING ADATEXIT,R12 Establish R12 as base register. STM R14,R12,12(R13) Save caller's registers. LR R12,R15 Temporarily save register 15. LR R2,R1 Temporarily save register 1. BAS R1,TES00001 LEN00001 DC AL4(WORKLENG) Length of workarea. TES00001 DS 0H L R0,0(,R1) Supply length of workarea. STORAGE OBTAIN, Obtain Storage for the workarea. X LENGTH=(R0), Length of workarea in R0. X SP=0, Obtain in sub pool 0. X BNDRY=DBLWD, Storage to be alligned at doubleword X LOC=ANY boundary. ST R1,8(,R13) Store the forward pointer. LR R14,R1 Provide start address of storage. L R15,LEN00001 provide length of staorage. XR R0,R0 Clear register 0. XR R1,R1 Clear register 1. MVCL R14,R0 Initialize the storage to X'00'. L R1,8(,R13) Restore back register 13.

Addressing

Address is used to refer each byte in VIRTUAL StorageMaximum VIRTUAL Storage is 2GB – 231

Hence an Address on OS/390 is represented in a FULLWORD i.e. 4 bytes or 32 bitsWhere is the 1 bit missing?

Addressing

In original MVS versions maximum virtual memory was 16MB – 224 (The LINE)From MVS/XA onwards this was enhanced to 2GB – 231 To provide backward compatibility, one bit was reserved 1 – indicates 31 bit addressing 0 – indicates 24 bit addressing

Addressing

This addressing is also called AMODE AMODE 24 and 31 AMODE goes hand-in-hand with where data

is located/residing in virtual storage

This residency is called RMODE RMODE 24 and ANY RMODE 24 forces data to reside below the

line RMODE ANY causes data to reside below the

line if storage available, else above the line

Possible AMODE/RMODE combinations 24/24, 31/24, 31/ANY 24/ANY not possible

Addressing

Any location is always translated into base and displacement formAbs Addr = Base Addr + DisplacementEstablishing a base is also called ADDRESSABILITYAssembler requires to establish addressability, if items need to be addressed with location names

Registers

IBM provides many types of REGISTERS General Purpose Registers (GPRs) Floating Point Registers (FPRs) Control Registers (CRs) Access Registers (ARs)

We will restrict to GPRs which are mainly used in application programming16 GPRs – numbered 0 thru 15Each GPR is 4 bytes long i.e. 32 bits

Registers

Used as Base Registers i.e. point to some base

location Index Registers i.e. contain a value to

index into, from base location

Now, Abs Addr = Base Reg + Index Reg +

Displacement

Machine Instructions

Based on types of OPERANDSRR – Register-RegisterRX – Register-IndexRS – Register-StorageSI – Storage-ImmediateS – StorageSS1 – Storage-Storage Type 1

SS2 – Storage-Storage Type 2

Machine Instructions

First byte of instruction has OPCODE (Operation Code)Following bytes are operandsRegisters (Base or Index) take 4 bits i.e. nibble i.e. half wordDisplacement requires 12 bits i.e. 3 nibblesImmediate operands require 1 byte i.e. 8 bitsLength requires 1 byte (with exception od SS2 instruction type where 2 lengths are stored in 1 byte)

Machine Instructions0 8 12

RR R1 R2

0 8 12 16 20

RX R1 X2 B2

0 8 12 16 20

RS R1 R2 B3

0 8 16 20

SI B1

0 16 20

S B1

0 8 16 20 32 36

SS1 B1 B1

0 8 12 16 20 32 36

SS2 L1 L2 B1 B2Opcode D1 D2

D1D1Opcode L

Opcode D1

D1

I2

Opcode

Opcode

Opcode D2

Opcode D3

Data Types

Hexadecimal X (1 Byte)Character C (1 Byte)Binary B (1 Byte)Halfword H (2 Bytes)Fullword F (4 Bytes)DoubleWord D (8 bytes)Address Absolute A (4 Bytes)External Address V (4 Bytes)Packed P (1 Byte)

Data TypesEach data type follows its boundary alignmentFullword, Address (External and Absolute) are aligned at FULLWORD boundary i.e. stored at an address divisible by 4Halfword is aligned at HALFWORD boundary i.e. stored at an address divisible by 2Character, Hexadecimal, Packed and Binary are aligned at byte boundary i.e. stored at an address divisible by 1Doubleword is aligned at DOUBLEWORD boundary i.e. stored at an address divisible by 8

Data Definition

DS – Define Storage Label DS X

DC – Define Constants Label DC C’1’

With DC an initial value can be specifiedExact format is

Label DS/DC Duplicator_Type_Modifier_Initial PGMNAME DC 1CL8’TESTPROG’

Duplicator – 1 Type – C for Character Modifier - L8 indicating length of 8 Initial – ‘TESTPROG’

Data Definition

VAR1 DS C Define a character storageVAR2 DS C’A’ Define a character constant initialized with ‘A’VAR3 DS CL10 Define a character storage of length 10VAR4 DS 2CL10 Define 2 character storages of length 10VAR5 DS FL1 Define a fullword storage of length 1

Data Definition

Fullword is 4 bytes – Why Length 1 ? VAR1 DS C /*Start address 0000FF00*/ VAR2 DS F /*Start address 0000FF04*/

Assembler will insert 3 bytes to do the boundary alignmentTo avoid boundary alignment, specify the ModifierVARX DC C’ABC’ /*3 byte constant*/Same as VARX DC CL3’ABC’

Assembler Program Start

CSECT Is an Assembler Instruction indicating start

of an executable control section LABEL CSECT LABEL is equivalent to the PGMID in COBOL CSECT is aligned on a double word

boundary Multiple CSECT can be mentioned in the

same program CSECT ends at start of another CSECT or

END statement

LOAD/STORE/MOVE/BRANCH Instructions

LOAD – RX Type The LOAD instruction takes four

bytes from storage or from a general register and place them unchanged into a general purpose register. Abbreviated as “L”. Instruction format:

L R1,D2(X2,B2)

Examples of LOAD Instruction L R6,4(R5,R12) LOAD R6 FROM R5 ADDRESS + R12

ADDRESS + 4 L R14,FULLWORD

LOAD R14 FROM "FULLWORD"

Various LOAD Instructions

LA (LOAD ADDRESS) LM (LOAD MULTIPLE) LH (LOAD HALFWORD) LR (LOAD REGISTER)

LOAD ADDRESS – RX Type

The LOAD ADDRESS instruction loads the address specified by the second operand into the general purpose register specified by the first operand. Abbreviated as “LA”.Instruction format:

LA R1,D2(X2,B2)

Examples of LA Instruction LA R6,4(R5,R12) LOAD R6 WITH R5 ADDRESS + R12 ADDRESS + 4 LA R14,1(,R14) ADD 1 TO VALUE IN R14

LOAD MULTIPLE – RS Type

The LOAD MULTIPLE instruction loads 1 or more registers from consecutive fullword storage locations addressed by the second operand of the instruction. Abbreviated as “LM”.Instruction format:

LM R1,R3,D2(B2)

Example for LM Instruction LM R14,R12,12(R13) LOAD REGISTERS 14 THROUGH 12

FROM 15 CONSECUTIVE WORDS AT ADDRESS IN R13 PLUS DECIMAL 12

LOAD HALFWORD – RX Type

The LOAD HALFWORD instruction places unchanged a halfword from storage into the right half of a register. The left half of the register is loaded with zeros or ones according to the sign (leftmost bit) of the halfword. Abbreviated as “LH”.Instruction format:

LH R1,D2(X2,B2)

Examples of LH Instruction LH R6,0(0,14)Register 14 contains 00 00 18 03. Locations 1803-1804 contain 00 20. After the instruction is executed, register

contains 00 00 00 20. If locations 1803-1804 had contained a negative number, for example, A7 B6, a minus sign would have been propagated to the left, giving FF FF A7 B6 as the final result in register 6.

LOAD REGISTER – RR Type

The LOAD REGISTER instruction copies a value from one general purpose register into another. Any general purpose register may be used as the R1 or R2 operands. Abbreviated as “LR”.Instruction format:

LR R1,R2

Examples of LR Instruction LR R6,R5 COPY R5 INTO R6 LR R7,R7 COPY R7 INTO ITSELF

INSERT CHARACTER–RX Type

The INSERT CHARACTER instruction inserts the single byte addressed by the second operand into the rightmost byte (bits 55-63) of the first operand register. The remaining bytes of the first operand register remain unchanged. Abbreviated as “IC”Instruction format:

IC R1,D2(X2,B2)

Examples of IC Instruction IC R11,=C' ‘ INSERT LITERAL CONSISTING OF A SINGLE BLANK INTO RIGHTMOST BYTE OF R11 IC R2,0(R3,R8) INSERT BYTE AT ADDRESS IN R3 + ADDRESS IN R8 INTO RIGHTMOST BYTE OF

R2

INSERT CHARACTERS UNDER MASK – RS Type

The INSERT CHARACTERS UNDER MASK (ICM) instruction may be used to replace all or selected bytes in a general register with bytes from storage and to set the condition code to indicate the value of the inserted field. Abbreviated as “ICM”.Instruction format:

ICM R1,M3,D2(B2)

Examples for ICM Instruction ICM R5,B'0111',FIELDA FIELDA: FE DC BA Register 5 (before): 12 34 56 78

Register 5 (after): 12 FE DC BA

Condition code (after): 1 (leftmost

bit of inserted field is one)

Example 2 for ICM ICM 6,B'1001',FIELDB FIELDB: 12 34 Register 6 (before): 00 00 00 00

Register 6 (after): 12 00 00 34

Condition code (after): 2 (inserted

field is nonzero with leftmost zero bit)

STORE Instruction – RX Type

The STORE instruction stores the rightmost four bytes of a general purpose register (the R1 value) at a fullword location in main storage.Abbreviated as “ST”.Instruction format

ST R1,D2(X2,B2)

Examples for ST Instruction ST R6,4(R5,R12)

STORE RIGHT 4 BYTES IN R6 AT R5 ADDRESS + R12 ADDRESS + 4 ST R14,FULLWORD

STORE RIGHT 4 BYTES IN R14 AT "FULLWORD"

Various STORE Instructions

STH (STORE HALFWORD) STM (STORE MULTIPLE) STC (STORE CHARACTER) STCM (STORE CHARACTER UNDER

MASK)

STORE HALFWORD – RX Type

The STORE HALFWORD instruction stores the rightmost 2 bytes (bits 48-63) of a general purpose register (the R1 value) into a 2 byte halfword in main storage. Abbreviated as “STH”.Instruction format:

STH R1,D2(X2,B2)

Examples for STH Instruction STH R2,0(,R4) STORE RIGHT MOST TWO BYTES OF

R2 IN R4 STH R14,HALFWORD STORE 2 BYTES IN R14 IN

"HALFWORD"

STORE MULTIPLE – RS Type

The STORE MULTIPLE instruction stores the rightmost four bytes of one or more general purpose registers at consecutive fullword storage locations addressed by the second operand of the instruction. Abbreviated as “STM”.Instruction format:

STM R1,R3,D2(B2)

Example for STM Instruction STM R14,R12,12(R13) STORE RIGHT HALF OF REGISTERS 14

THROUGH 12 AT 15 CONSECUTIVE WORDS AT ADDRESS IN R13 PLUS DECIMAL 12

STORE CHARACTER– RX Type

The STORE CHARACTER instruction stores bits 56-63 (rightmost byte) of the general purpose register specified by the first operand at the second operand address. Abbreviated as “STC”.Instruction format:

STC R1,D2(X2,B2)

Examples for STC instruction STC R8,BYTE STORE RIGHTMOST BYTE OF R8 AT LABEL "BYTE" STC R14,4(,R6) STORE RIGHTMOST BYTE OF R14 4 BYTES PAST ADDRESS IN R6

STORE CHARACTER UNDER MASK – RS Type

The STORE CHARACTERS UNDER MASK instruction stores selected bytes from the first operand register into Consecutive bytes addressed by the second operand.Abbreviated as “STCM”.Instruction format:

STCM R1,M3,D2(B2)

Example for STCM Instruction STCM 8,B'0111',FIELD3 Register 8: 12 34 56 78 FIELD3 (before): not significant FIELD3 (after) : 34 56 78

MOVE Instructions

Various MOVE Instructions are MVC (MOVE CHARACTER) MVCIN (MOVE INVERSE) MVCL (MOVE LONG) MVI (MOVE IMMEDIATE) MVZ (MOVE ZONES) MVN (MOVE NUMBERIC)

MOVE CHARACTER– SS1 Type

The MOVE CHARACTER instruction moves from 1 to 256 bytes from one main storage location to another. The storage locations may overlap each other. If the length operand is not explicitly specified in the first operand, the implicit length of the first operand symbol is used. Abbreviated as “MVC”.Instruction format:

MVC D1(L1,B1),D2(B2)

Examples for MVC Instruction MVC 10(256,R5),0(R5) MOVE 256 BYTES FROM R5 ADDRESS

TO R5 PLUS 10 (DECIMAL) ADDRESS MVC TITLE(7),=C'1 ERROR‘ MOVE 7 BYTE LITERAL TO "TITLE" ADDRESS

MOVE INVERSE – SS1 Type

The MOVE INVERSE instruction moves the bytes at the second operand location to the first operand location, simultaneously reversing the order of the bytes. After the MOVE INVERSE completes, the rightmost byte of the second operand is the leftmost byte of the first operand. Abbreviated as “MVCIN”.Instruction format:

MVCIN D1(L1,B1),D2(B2)

Example for MVCIN Instruction MVCIN 10(128,R3),0(R5) MOVE 128 BYTES AT ADDRESS IN R5 TO R3 ADDRESS +10 AND REVERSE THEIR ORDER

Note: R5 address should contain the the rightmost byte of the field to be moved.

MOVE CHARACTER LONG – RR Type

MOVE CHARACTER LONG instruction moves from 1 to 2,147,483,647 bytes in main storage. Both operands must designate an even-numbered register of an even-odd register pair. The first operand even numbered register contains the address of the receiving field. The first operand odd numbered register contains the length of the receiving field.

MVCL

The second operand even numbered register contains the address of the sending field. The second operand odd numbered register contains the length of the sending field in the right 3 bytes and an optional padding character in the leftmost byte. The padding character is used to pad the receiving field if the second operand length is less than the first operand length.

MOVE IMMEDIATE – SI Type

The MOVE (MVI) instruction places one byte of information from the instruction stream into storage. The byte may be any type of constant or an expression that resolves to a value in the range 0 to 255. Abbreviated as “MVI”.Instruction format:

MVI D1(B1),I2

Examples for MVI Instruction MVI 10(R4),X'10' MOVE A X'10' TO R4+X'10‘ MVI SWITCH,C' ' MOVE A BLANK TO 'SWITCH‘

MOVE ZONE – SS1 Type

The leftmost four bits of each byte(zone portion) in the second operand are placed in the leftmost four bit positions(zone portion) of the corresponding bytes in the first operand. The rightmost four bits of each byte in the first operand remain unchanged. Abbreviated as “MVZ”.Instruction format:

MVZ D1(L1,B1),D2(B2)

Example for MVZ Instruction MVZ 10(128,R3),0(R5) MOVE ZONE PORTION OF 128 BYTES FROM R5 ADDRESS TO R3 ADDRESS

+ 10

MOVE NUMERIC – SS1 Type

The rightmost four bits of each byte(numeric portion) in the second operand are placed in the rightmost 4 bit positions(numeric portion) of the corresponding bytes in the first operand. The leftmost four bits of each byte in the first operand remain unchanged. Abbreviated as “MVN”.Instruction format:

D1(L1,B1),D2(B2)

Example for MVN Instruction MVN 10(128,R3),0(R5) MOVE NUMERICS OF 128 BYTES

FROM R5 ADDRESS TO R3 + 10

BRANCH Instructions

Various BRANCH Instructions B (BRANCH) BC (BRANCH ON CONDITION) BCT (BRANCH ON COUNT) BCTR (BRANCH ON COUNT REGISTER) BAL (BRANCH AND LINK) BAS (BRANCH AND SAVE) BSM (BRANCH AND SET MODE) BASR (BRANCH AND SAVE REGISTER) BAKR (BRANCH AND STACK) BASSM (BRANCH AND SAVE AND SET MODE)

Unconditional BRANCH Instructions

BRANCH (B)BRANCH REGISTER (BR)

Conditional BRANCH Instructions

BH or BHR - Branch on A High BL or BLR - Branch on A Low BE or BER - Branch on A Equal B BO or BOR - Branch on Overflow BP or BPR - Branch on Plus BM or BMR - Branch on Minus BZ - Branch on Zero

BRANCH Instruction Format

XXX D2(X2,B2) XXXR R2 XXX label XXXXL label

where XXX is the mnemonicbranch instruction

Examples for BRANCH Instruction B 4(R15) UNCONDITIONAL BRANCH TO ADDRESS

IN R15 + 4 BH LOOPA BRANCH TO "LOOPA" LABEL IF FIRST COMPARED OPERAND IS HIGH BR R1 UNCONDITIONAL BRANCH TO ADDRESS IN

R1

BRANCH ON COUNT

The BRANCH ON COUNT instruction is used to branch to a storage location whose address is specified by the second operand of the instruction, if the value in the first operand register is non-zero after one is subtracted from it.Abbreviated as “BCT”.Instruction format:

BCT R1,D2(X2,B2)

Examples for BCT Instruction BCT R4,100(,R11) BRANCH TO ADDRESS IN R11 PLUS

100 BYTES IF R4 VALUE MINUS ONE IS

NOT ZERO BCT R5,ENDOFILE BRANCH TO "ENDOFILE" LABEL IF R5 MINUS 1 IS NOT ZERO

BRANCH ON COUNT REGISTER

The BRANCH ON COUNT REGISTER instruction is used to branch to a storage location whose address is specified by the second operand of the instruction, if the value in the first operand register is non-zero after one is subtracted from it.Abbreviated as “BCTR”.Instruction format:

BCTR R1,R2

Examples for BCTR Instruction BCTR R4,R15

BRANCH TO ADDRESS IN R15 IF R4 VALUE MINUS ONE IS NOT ZERO BCTR R5,0 DECREMENT R5 BY 1, BUT DO NOT BRANCH

BRANCH AND LINK – RX Type

The BRANCH AND LINK instruction causes program execution to branch to the address provided by the second operand. Linkage information is saved in the first operand register after the branch address has been computed. When the R2 value specifies R0, no branch is taken. Linkage Information – Address of next sequential instruction, Instruction length code, Condition code etc. Abbreviated as “BAL”.

Instruction format: BAL R1,D2(X2,B2)

Example for BAL Instruction BAL R14,CALCVAL BRANCH TO "CALCVAL" LABEL- SAVE

ADDRESS OF NEXT INSTRUCTION IN

R14

BRANCH AND LINK – RR Type

The BRANCH AND LINK REGISTER instruction causes program execution to branch to the address in the second operand register. Linkage information is saved in the first operand register after the branch address has been computed. Abbreviated as “BALR”.Instruction format:

BALR R1,R2

Example for BALR Instruction BALR R14,R15 SAVE LINK INFO IN R14 AND

BRANCH TO ADDRESS IN R15

BRANCH AND SAVE – RX Type

Information from the current PSW, including the updated instruction address, is saved as link information at the first-operand location. Subsequently, the instruction address in the PSW is replaced by the branch address. In the RX format(BAS), the second-operand address is used as the branch address. In the RR format(BASR), the contents of general register R2 are used to generate the branch address; however, when the R2 field is zero, the operation is performed without branching.

Example for BAS Instruction BAS R14,CALCVAL BRANCH TO "CALCVAL" LABEL - SAVE ADDRESS OF NEXT INSTRUCTION IN R14

Example for BASR Instruction BASR R14,R15 BRANCH TO ADDRESS IN R15 - SAVE

ADDRESS OF NEXT INSTRUCTION IN R14

Basic Assembler Program

Start Program - CSECTEntry Housekeeping InstructionsProcessingExit Housekeeping InstructionsData DefinitionsEnd program - END

Basic Assembler ProgramEntry Housekeeping InstructionsUSING

Used to establish Addressability USING LABEL/*,REGISTER Indicates the specified register now points to the

given label and henceforth will be used as base for the area

NOTE: Responsibility of the programmer to load register with the correct address of the label

If multiple registers are pointing to an area i.e. used to establish base, then one with lowest offset is used

A single base register can provide addressability to 4K i.e. 4096 bytes (NOTE: 12 Bit displacement in Instructions)

If need to access variables beyond 4K offset, multiple base registers need to be used

USING LABEL,Rx,Ry USING LABEL+4096,Ry

Basic Assembler Program Registers are common resource and need to

be preserved Caller has called us with some register

contents, need to save them IBM’s convention

R15 – Points to Called Programs Address R14 – Caller’s Return Address R1 – Address of parameter list

Addressability needs to be established so that locations can be referenced

Where to save ???? CALLER’s SAVEAREA SAVEAREA – An area in the CALLED Module

requiring 18F R13 points to SAVEAREA as per IBM’s convention

Basic Assembler Program

0 Used by PL/I4 Address of Caller's Savearea Placed by P, after X called P8 Address of Called Program's Savearea Placed by Q, after P calls Q

12 Register 1416 Register 1520 Register 024 Register 128 Register 232 Register 336 Register 440 Register 544 Register 648 Register 752 Register 856 Register 960 Register 1064 Register 1168 Register 12

Contents of Program P's Registers placed here by program

Q after P Calls Q

Program X calls Program P and Program P calls Program XProgram P's SAVEAREA Contents

Basic Assembler ProgramEntry HouseKeeping

USING TESTDCB,R12 ESTABLISH R12 AS BASE REG STM R14,R12,12(R13) SAVE CALLER'S REGS LR R12,R15 LOAD BASE REG, R15=CALLER ADDRESS ST R13,SVAREA+4 SAVE CALLER SAVEAREA POINTER LR R2,R13 TEMPORARY LOAD CALLER SAVEAREA LA R13,SVAREA LOAD ADDRESS OF PROGRAM’S SAVEAREA ST R13,8(R2) SAVE PROGRAM SAVEAREA IN

CALLER

Exit HouseKeeping L R13,SVAREA+4 RESTORE CALLER SAVEAREA LM R14,R12,12(R13) RESTORE CALLER'S REGS L R15,=F’0’ INITIALIZE RETURN CODE BR R14 BRANCH TO RETURN ADDRESS

Basic Assembler Program TESTPROG CSECT USING TESTDCB,R12 ESTABLISH R12 AS BASE REG STM R14,R12,12(R13) SAVE CALLER'S REGS LR R12,R15 LOAD BASE REG, R15=CALLER ADDRESS ST R13,SVAREA+4 SAVE CALLER SAVEAREA POINTER LR R2,R13 TEMPORARY LOAD CALLER SAVEAREA LA R13,SVAREA LOAD ADDRESS OF PROGRAM’S SAVEAREA ST R13,8(R2) SAVE PROGRAM SAVEAREA IN CALLER ----------------------------- ----------------------------- L R13,SVAREA+4 RESTORE CALLER SAVEAREA LM R14,R12,12(R13) RESTORE CALLER'S REGS L R15,=F’0’ INITIALIZE RETURN CODE BR R14 BRANCH SVAREA DS 18F END TESTPROG

Basic Assembler ProgramProcessing – I/O to PS

OPEN Macro Used to open a file OPEN (INFILE,INPUT,OUTFILE,OUTPUT) GET macro used to read one record GET INFILE,TEMPAREA PUT macro used to write one record PUT OUTFILE,OUTAREA CLOSE macro used to write one record CLOSE (INFILE,,OUTFILE) DCB macro used to define a file INFILE DCB DDNAME=INPFILE0, MACRF=(GM),

DSORG=PS,LRECL=25,BLKSIZE=2500, RECFM=FB,EODAD=MAIN$015,SYNAD=ERRFILE

MACRF – GM for GET and PM for Put EODAD – Indicates End Of File Routine name SYNAD – Indicates Error Analysis Routine Address

Basic Assembler ProgramMAIN$000 DS 0H OPEN (INFILE,INPUT,OUTFILE,OUTPUT) X OPEN THE INPUT & OPTPUT FILES LTR R15,R15 Q. OPEN SUCCESSFUL? BNZ ERROPEN A. NO, PROCESS OPEN ERROR GET INFILE,TEMPAREA READ THE INPUT FILE PUT OUTFILE,TEMPAREA WRITE THE OUTPUT FILE CLOSE (INFILE,,OUTFILE) CLOSE THE INPUT AND OUTPUT FILES----------------MAIN$015 DS 0H STH R6,OUTAREA+64 STORE THE NUMBER OF TRAILERS STH R9,OUTAREA STORE THE TOTAL REC LEN IN RDW PUT OUTFILE,OUTAREA WRITE THE OUTPUT FILE CLOSE (INFILE,,OUTFILE) CLOSE THE INPUT AND OUTPUT FILES LTR R15,R15 Q. CLOSE SUCCESSFUL? BNZ ERRCLOSE A. NO, PROCESS CLOSE ERROR B RETURN A. YES, EXIT THE PROGRAM ERRFILE ABEND 500,DUMPERRCLOSE ABEND 500,DUMPINFILE DCB DDNAME=INPFILE0,MACRF=(GM),DSORG=PS,LRECL=25, X BLKSIZE=2500,RECFM=FB,EODAD=MAIN$015,SYNAD=ERRFILEOUTFILE DCB DDNAME=OUTFILE0,MACRF=(PM),DSORG=PS,LRECL=300, X BLKSIZE=2500,RECFM=FB,EODAD=MAIN$015,SYNAD=ERRFILE

BIT Manipulation Instructions

AND (N)AND IMMEDIATE (NI)OR (O)OR IMMEDIATE (OI)EXCLUSIVE OR (X)EXCLUSIVE OR IMMEDIATE (XI)

AND

The AND instruction ANDs the contents of the four bytes addressed by the second operand with the contents of the first operand register. The logical AND function is applied bit by bit; a bit in the first operand register is set to one if both corresponding bits in the first and second operands are one. Abbreviated as “N”.Instruction format:

N R1,D2(X2,B2)

AND function table

2nd Operand Bit Values 0 1 +--------+--------+ | | | 0 | 0 | 0 | 1st | | | Operand +--------+--------+ Bit | | | Values 1| 0 | 1 | | | | +--------+--------+

Examples for AND Instruction N R3,1000(R2,R6) AND VALUE IN R3 WITH 4 BYTES AT

R2 ADDRESS + R6 ADDRESS + 1000 decimal

N R7,=F'32767' AND VALUE IN R7 WITH LITERAL

32,767

AND IMMEDIATE

The AND instruction logically ‘ANDS' the contents of the one byte addressed by the second operand with the byte of data specified in the instruction. Abbreviated as “NI”.Instruction format:

NI D1(B1),I2

Examples for NI Instruction NI BYTE1,X'0F‘ AND VALUE AT BYTE1 WITH

IMMEDIATE BYTE OF X'0F' NI 0(R10),255 AND VALUE AT R10 ADDRESS PLUS 0 WITH IMMEDIATE BYTE OF 255

DECIMAL

OR

The O instruction performs a connective logical Boolean "OR" function between the 4 bytes in the register specified by the first operand, and the 4 bytes in storage addressed by the second operand. Abbreviated as “O”.Instruction format:

O R1,D1(X2,B2)

OR function table


Examples for OR Instruction O R3,0(,R6) "OR" R3 WITH 4 BYTES AT ADDRESS

IN R6 O R12,=X'00FF00FF' "OR" R12 WITH 4 BYTE

HEXADECIMAL CONSTANT

OR IMMEDIATE

The OI instruction performs a logical connective Boolean “OR" function between the byte addressed by the first operand, and the byte of immediate data specified by the second operand. Abbreviated as “OI”.Instruction format:

OI D1(B1),I2

Examples for OI Instruction OI 0(R4),X'40' "OR" BYTE ADDRESSED BY R4 WITH HEX LITERAL OI FLAGBYTE,X'80' "OR" "FLAGBYTE" WITH A X'80'

(DECIMAL 128)

EXCLUSIVE OR

The EXCLUSIVE OR instruction performs a logical Boolean exclusive "OR" function between the 4 bytes in the right half of the register specified by the first operand, and the 4 bytes in storage addressed by the second operand. Abbreviated as “X”.Instruction format:

X R1,D1(X2,B2)

EXCLUSIVE OR function table


Examples for EXCLUSIVE OR Instruction X R3,0(,R6) EXCLUSIVE "OR" R3 WITH 4 BYTES

AT ADDRESS IN R6

X R12,=X'00FF00FF' EXCLUSIVE "OR" R12 WITH 4 BYTE HEXADECIMAL CONSTANT

EXCLUSIVE OR IMMEDIATE

The EXCLUSIVE OR IMMEDIATE instruction performs a logical Boolean exclusive "OR" function between the byte addressed by the first operand, and the byte of immediate data specified by the second operand. Abbreviated as “XI”.Instruction format:

XI D1(B1),I2

Examples for XI Instruction XI 0(R4),X'40' EXCLUSIVE "OR" BYTE ADDRESSED BY R4 WITH HEX ITERAL

XI FLAGBYTE,X'80' EXCLUSIVE "OR" "FLAGBYTE" WITH A X'80' (DEC. 128)

SHIFT LEFT ALGEBRIC – RS Type

The SHIFT LEFT ALGEBRAIC instruction left shifts the 31-bit numeric portion of the 32-bit signed value in the rightmost bits of the register specified by the first operand.The number of bits to shift left are specified

by the right six bits of the address specified by the second operand. The maximum shift amount is 63 decimal. Bits 0-31 of general register R1 remain unchanged.

Condition code for SLA

Condition code 0 is set if the resultant value after shifting is 0. Condition code 1 is set if the resultant value after shifting is less than 0. Condition code 2 is set if the resultant value after shifting is greater than 0. Condition code 3 is set if arithmetic overflow occurs.

The sign of the first operand remains unchanged. All 31 numeric bits of the operand participate in the left shift. Abbreviated as “SLA”.Instruction format: SLA R1,D2(B2)

Examples for SLA Instruction If the contents of register 2 are: 00 7F 0A 72 = 00000000 01111111 00001010 01110010SLA R2,8(R0)Results in register 2 being shifted left eight bit

positions. Hence the new content is 7F 0A 72 00 = 01111111 00001010 01110010

00000000

SLA R10,12 SHIFT 31 BITS IN R10 LEFT 12 BIT POSITIONS

SHIFT LEFT LOGICAL – RS Type

The SHIFT LEFT LOGICAL instruction left shifts the 32-bit value in the rightmost bits of the register specified by the first operand. The number of bits to shift left are specified by the right six bits of the address specified by the second operand. Bits 0-31 of general register R1 remain unchanged. Abbreviated as “SLL”.

For SLL, the first operand is in bit positions 32-63 of general register R1. All 32 bits of the operand participate in the left shift.The condition code is not set by this instruction. Instruction format:SLL R1,D2(B2)

Example for SLL Instruction SLL R12,22 SHIFT 32 BITS IN R12 LEFT 22 BIT POSITIONS

SHIFT RIGHT ARITHMETIC – RS Type

The SHIFT RIGHT ALGEBRAIC instruction right shifts the 31-bit numeric portion of the 32-bit signed value in the rightmost bits of the register specified by the first operand. The number of bits to shift right are specified by the right six bits of the address specified by the second operand. The maximum shift amount is 63 decimal.

The sign of the first operand remains unchanged. All 31 numeric bits of the operand participate in the right shift. Abbreviated as “SRA”.Instruction format: SRA R1,D2(B2)

Condition code for SRA

Condition code 0 is set if the resultant value after shifting is 0. Condition code 1 is set if the resultant value after shifting is less than 0. Condition code 2 is set if the resultant value after shifting is greater than 0.

Example for SRA instruction SRA R10,12 SHIFT 31 BITS IN R10 RIGHT 12 BIT

POSITIONS

SHIFT RIGHT LOGICAL – RS Type

The SHIFT RIGHT LOGICAL instruction right shifts the 32-bit value in the rightmost bits of the register specified by the first operand. The number of bits to shift right are specified by the right six bits of the address specified by the second operand. The maximum shift amount is 63 decimal. All 32 bits of the operand participate in the right shift.

Abbreviated as “SRL”.Instruction formatSRL R1,D2(B2)

Example for SRL Instruction SRL R10,12 SHIFT 32 BITS IN R10 RIGHT 12 BIT POSITIONS

Arithmetic Instructions

ADD (A)SUBTRACT (S)MULTIPLY (M)DIVIDE (D)

ADD – RX Type

The ADD instruction algebraically adds the value addressed by the second operand to the contents of the first operand register. Abbreviated as “A”.Instruction format

A R1,D2(X2,B2)

Examples for ADD Instruction A R3,24(R5,R12) ADD CONTENTS AT R5 ADDRESS +

R12 ADDRESS + 24 TO R3

A R14,FULLWORD ADD "FULLWORD" TO R14 A R0,=F'1' ADD 1 TO R0

Condition Code after ADD

Condition code 0 is set if the result of the add is 0. Condition code 1 is set if the result of the add is less than 0. Condition code 2 is set if the result of the add is greater than 0. Condition code 3 is set if overflow occurs.

ADD REGISTER – RR Type

The ADD REGISTER instruction algebraically adds the value in the second operand register to the contents of the first operand register.Abbreviated as “A”.Instruction format

AR R1,R2

Examples for AR Instruction AR R3,R2 ADD QUANTITY IN R3 TO R2

AR R8,R8 ADD VALUE IN R8 TO ITSELF

SUBTRACT – RX Type

The SUBTRACT instruction subtracts the value addressed by the second operand from the contents of the first operand register. Abbreviated as “S”.Instruction format:

S R1,D2(X2,B2)

Examples for SUBTRACT Instruction S R3,24(R5,R12) SUBTRACT CONTENTS AT R5 ADDRESS +

R12 ADDRESS + 24 FROM R3

S R14,FULLWORD SUBTRACT "FULLWORD" FROM R14

S R0,=F'1' SUBTRACT 1 FROM R0

SUBTRACT REGISTER – RR Type

The SUBTRACT REGISTER instruction subtracts the value in the second operand register from the contents of the first operand register. Abbreviated as “SR”.Instruction format:

SR R1,R2

Examples for SR Instruction SR R3,R2 SUBTRACT CONTENT IN R2 FROM R3

SR R8,R8 SUBTRACT VALUE IN R8 FROM ITSELF

(RESULT IS 0)

MULTIPLY – RX Type

The MULTIPLY instruction multiplies the value in the odd-numbered register of the first operand register pair by the value in the word at the second operand address. The first operand must designate an even-odd register pair. The initial contents of the even-numbered register are ignored; the result of the multiplication occupies the first operand even-odd register pair.

Abbreviated as “M”.Instruction format:

M R1,D2(X2,B2)Examples for MULTIPLY Instruction M R2,0(R5,R6) MULTIPLY VALUE IN R2 BY VALUE IN WORD

AT ADDRESS IN R5 + ADDRESS IN R6 M R8,=F'100' MULTIPLY VALUE IN R9 BY LITERAL 100

(DECIMAL)

MULTIPLE REGISTER – RR Type

The MULTIPLY REGISTER instruction multiplies the value in the odd-numbered register of the first operand register pair by the value in the second operand register.The first operand must designate an even-odd register pair. The second operand may designate any general purpose register. Abbreviated as “MR”.

Instruction format: MR R1,R2

Examples for MR Instruction MR R2,R5

MULTIPLY VALUE IN R3 BY VALUE IN R5 MR R8,R9

MULTIPLY VALUE IN R9 BY ITSELF (SQUARING VALUE)

DIVIDE – RX Type

The DIVIDE instruction divides the fullword value addressed by the second operand (the divisor) into the 64-bit signed value designated by the first operand (the dividend). The first operand must specify the even-numbered register of an even-odd register pair.Abbreviated as “M”.Instruction format:D R1,D2(X2,B2)

The leftmost 32 bits of the dividend are in bit positions 32-63 of the even-numbered general register specified by the first operand, and the rightmost 32 bits of dividend are in bit positions 32-63 of the odd-numbered general register associated with the first operand. After the division, the remainder (if any) and quotient are contained in the right halves of the even and odd numbered registers, respectively. The left halves of the registers remain unchanged.

Abbreviated as “D”.Instruction format:D R1,D2(X2,B2)

Example for DIVIDE Instruction D R6,=F'300' DIVIDE VALUE IN REGISTER R6-R7 BY

A FULLWORD DECIMAL 300

DIVIDE REGISTER – RR Type

The DIVIDE REGISTER instruction divides the fullword value in the second operand register into the 64-bit signed value which the even-odd register pair designated by the first operand contains. After the division, the remainder (if any) and quotient are contained in the even and odd numbered registers, respectively. Abbreviated as “DR”.

Instruction format: DR R1,R2

Examples for DR Instruction DR R6,R9 DIVIDE 64-BIT VALUE IN RIGHT HALVES OF

REGISTERS R6 & R7 BY FULLWORD

VALUE IN R9

The ZERO AND ADD PACKED instruction copies the packed field at the second operand address on top of the packed field at the first operand address.The second operand field must be in the packed format; the first operand field can be in any format. Zeros are used to fill in the first operand if it is longer than the second operand. Zero, -ve, +ve or decimal overflow condition code will be set.

Instruction Format: ZAP D1(L1,B1),D2(L2,B2)

ZAP – SS2 Type

Example for ZAP Instruction: P1 DC P’-38460’

P2 DS PL4::

ZAP P2,P1

Result : P2 : 00 38 46 0D

Condition code 1 (-ve) is set.

ZAP – SS2 Type

MVN – SS1 Type

The MOVE NUMERICS instruction moves the numeric portion (right half) of each byte at the second operand address to corresponding positions of the byes at the first operand address. Each operand is processed left to right. The storage locations may overlap each other. Instruction Format: MVN D1(L1,B1),D2(B2)

Example for MVN Instruction:

P1 : F0 F1 F2 F3 F4 F5P2 : C6 C7 C8 C9::

MVN P1(4), P2Result :

P1 : F6 F7 F8 F9 F4 F5

MVN – SS1 Type

MVZ – SS1 Type

The MOVE ZONES instruction moves the zone portion (right half) of each byte at the second operand address to corresponding positions of the byes at the first operand address.Each operand is processed left to right. The storage locations may overlap each other. Instruction Format: MVZ D1(L1,B1),D2(B2)

MVZ – SS1 Type

Example for MVZ Instruction:

P1 : F6 F7 F8 F9 F4 C5

MVZ P1+5(1),=C’0’Result :

P1 : F6 F7 F8 F9 F4 F5

MVO – SS2 TypeThe MOVE WITH OFFSET instruction moves the second operand to the left of and adjacent to the rightmost four bits of the first operand. The result is obtained as if the operands were processed right to left. When necessary, the second operand is considered to be extended on the left with zeros. If the first operand is too short to contain all of the second operand, the remaining leftmost portion of the second operand is ignored.

Instruction Format: MVO D1(L1,B1),D2(L2,B2)

MVO – SS2 Type

Example for MVO Instruction:

P1 : 77 88 99 0C

MVO P1,=X’123456’

Result : P1 : 01 23 45 6C

SP – SS2 Type

The SUBTRACT PACKED subtracts the packed field pointed to by the second operand address from the packed field pointed to by the first operand address. Both the first and second operand fields being manipulated can be up to 16 bytes long.Zero, -ve, +ve or decimal overflow condition code will be set.

Instruction Format: SP D1(L1,B1),D2(L2,B2)

Example for SP Instruction:

P1 DC P’-45’ : :SP P1,=P’1’

Result : P1 : 04 6D

Condition code 1 (-ve) is set.

SP – SS2 Type

DP – SS2 Type

The first operand (dividend) is divided by the second operand (the divisor). The resulting quotient and remainder are placed at the first-operand location. The operands and results are in the packed format. The length in bytes of the divisor (2nd operand packed field) must be

less than 8 bytes, must also be less than the length in bytes of the dividend

Instruction Format: DP D1(L1,B1),D2(L2,B2)

The result of the division replaces the first operand packed field. The quotient is placed leftmost in the first operand packed field, with the remainder placed rightmost.

The length of the quotient is equal to the length of the dividend(L1) minus the length of the divisor(L2).

The length of the remainder is equal to the length of the divisor (L2).

The sign of the quotient is determined by the rules of algebra from the dividend and divisor signs. The sign of the remainder has the same value as the dividend sign. These rules hold even when the quotient or remainder is zero.

Condition code will not be set.

DP – SS2 Type

DP – SS2 Type

Example for DP Instruction: FIELD1 : 01 23 45 67 8C

FIELD2 : 32 1D

DP FIELD1,FIELD2

Result : FIELD 1 (after): 38 46 0D 01 8C

MP – SS2 Type

The product of the first operand (multiplicand) and the second operand (multiplier) is placed at the first-operand location. The operands and result are in the packed format.The length in bytes of the multiplier must be

less than 8 bytes, and must also be less than the length in bytes of the multiplicand

Instruction Format: MP D1(L1,B1),D2(L2,B2)

MP – SS2 Type

The multiplicand must have at least as many bytes of leftmost zeros as the number of bytes in the multiplier; otherwise, a data exception is recognized. This restriction ensures that no product overflow occurs. The product can't be bigger than 31 decimal digits, plus the sign. The leftmost decimal digit of the product will always be a zero.The multiplication is done using the laws of algebra, with the signs of both multiplicand and multiplier determining the sign of the product.

MP – SS2 Type

Example for MP Instruction: P1 DC P’-38460’ (Multiplicand)

P2 DC P’-321’ (Multiplier) P3 DS PL5

:ZAP P3,P1 (Extending the multiplicand

digits)MP P3,P2

Result : P3 (after): 01 23 45 66 0C

SRP – SS2 TypeThe first operand is shifted in the direction and for the number of decimal-digit positions specified by the second-operand address, and, when shifting to the right is specified, the absolute value of the first operand is rounded by the rounding digit, I3. Only the digit portion is shifted; the sign position does not participate in the shifting. Instruction Format: SRP D1(L1,B1),D2(B2),I3 D2 field specifies no. of positions to shift : +ve shift values specify shifting to the left. -ve shift values, which are represented in 2's

complement notation, specify shifting to the right.

Condition codes are set.

SRP – SS2 Type

Example for SRP Instruction: FIELD 3 (before): 12 39 60 0D

SRP FIELD3(4),64-3,5

Result : FIELD 3 (after): 00 01 24 0D

The rounding digit is added to the last digit shifted out (which is a 6), and the carry is propagated to the left. The sign is ignored during the addition.

The CONVERT TO DECIMAL instruction converts the 4-byte signed binary integer value in the rightmost half of the first operand register to an equivalent 8-byte packed decimal value at the second operand address. The second operand must designate a doubleword on a doubleword boundary. If the integer is +ve, the rightmost four bits of the packed decimal result is encoded as B'1100'; if –ve, as B'1101'.

Instruction Format: CVD R1,D2(X2,B2)

CVD – RX Type

CVD – RX TypeExample for CVD Instruction:

DWORD DC D’0’R10 contains 00 00 0F 0FCVD R10,DWORD

Result : DWORD: 00 00 00 00 00 03 85 5C (+3855)

CVB – RX TypeThe CONVERT TO BINARY instruction converts the 8-byte packed decimal value at the second operand address to an equivalent signed binary integer in the first operand register. The second operand must designate a doubleword on a doubleword boundary.

Instruction Format: CVB R1,D2(X2,B2)

CVD – RX TypeExample for CVB Instruction:

DWORD DS 0D DC PL8’25,594’

DWORD contains : 00 00 00 00 00 25 59 4C

CVD R10,DWORD

Result : R10 : 00 00 63 FA

PACK – SS2 Type

The PACK instruction converts the second operand field from zoned to packed decimal format by "packing" it into the field at the first operand address. Up to 16 bytes can be packed at once.Numeric part of each byte of second operand field is copied to the first operand field, except for the last byte, where both halves are copied, but swapped.

Instruction Format: PACK D1(L1,B1),D2(L2,B2)

Example for PACK Instruction:

P1 DS PL3 : :PACK P1,=X’F1F2F3C4’

Result : P1 : 01 23 4C

PACK – SS2 Type

UNPK – SS2 Type

The UNPACK instruction converts the second operand field from packed to zoned decimal format by "unpacking" it into the field at the first operand address. Up to 16 bytes can be unpacked at once. Swapping of last byte nibbles occurs.Instruction Format: UNPK D1(L1,B1),D2(L2,B2)

UNPK – SS2 Type

Example for UNPACK Instruction:

Z1 DS D : :UNPK Z1,=P’1234’

Result : Z1 : 00 00 00 F1 F2 F3 F4 C4

The EDIT instruction "unpacks“ converts to zoned format) the packed field pointed to by the second operand address, using a "pattern" that resides at the first operand address. (corr. to Picture Clause in Cobol)Instruction Format: ED D1(L1,B1),D2(B2)Pattern consists of bytes that contain the following hex values: X'20' - digit selector X'21' - significance starter X'22' - field separator Fill - fill character (any printable

character)

EDIT – SS1 Type

The first byte is called the Fill characterThe field separator identifies individual fields in a multiple-file editing operation. If either a digit selector or the significant starter is encountered it is replaced by The fill byte if the significance indicator is

OFF The unpacked source digit if the significance

indicator is ONIf any other byte is encountered, it is Replaced by fill byte if significance indicator

is OFF Remains unchanged if significance indicator

is ON

EDIT – SS1 Type (contd.)

The significance indicator is set to OFF At the start of the editing operation OR After a field separator is encountered OR After a source byte is examined that has a

plus code in the rightmost four bit positions. The significance indicator is turned on when A significant digit is encountered in the

source OR The significant starter is encountered in the

pattern



Example for ED InstructionPWORK DC X'4020206B212020' WORK DC P'6,456' WORK in packed format : 06456C

ED PWORK,WORK

WORK 0 6 4 5 6 PWORK (before) 20 20 6B 21 20 20

PWORK (after) 40 F6 6B F4 F5 F6 Result : 6 , 4 5 6

EDMK – SS1 Type (contd.)

The Edit and Mark instruction is identical in function to ED, except that the address of the leftmost 'significant' digit of the result is inserted in register 1 when EDMK completes execution, if a significant digit was found in the result. Register one is unchanged if no significant digit was found.Used to implement “floating” currency symbolInstruction Format: EDMK D1(L1,B1),D2(B2)

EDMK – SS1 Type (contd.)

Always ensure that R1 points to (Significant Starter + 1) location.Example for EDMK Instruction: To insert $ before the leftmost significant digit:

LA R1,PWORK+5 EDMK PWORK,WORK BCTR R1,0 MVI 0(R1),C'$'

Result : $ 6 , 4 5 6

MACROS

What is a macro? And what are its uses? Macro language is an extension of

assembler language. It provides a convenient way to generate a

sequence of assembler language statements many times in one or more programs.

A macro definition is written only once with sequence of assembler statements and can be invoked any where in the program.

Macro Uses

Uses Simplifies the coding of programs Reduces the chance of programming

errors Ensures that standard sequences of

statements are used to accomplish the functions we want.

assembler training

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