Hardware & I/O

Ch.4 – beginning on page 90

Ch.13 – Topic 1 & Topic 2

Representing Data

Positive Negative

Yes No

True False

On Off

1 0

RepresentingNumbers

Decimal Binary

(Base 10) (Base 2)

0 0

1 1

2 10

3 11

4 100

5 101

6 110

7 111

8 1000

9 1001

10 1010

11 1011

1000 1111101000

Representing Characters

• Extended ASCII 256 characters• EBCDIC 256 characters• UNICODE 64K characters

HI!

48 49 21

C8 C9 5A

? 16 bits each

ASCII

EBCDIC

UNICODE

Quantifying Bytes

1 Byte 8 bits

Kilobyte 210 bytes

Megabyte 220 bytes

Gigabyte 230 bytes

Terabyte 240 bytes

Petabyte 250 bytes

Exabyte 260 bytes

We deal with bytes all the time in programming. It seems that we are always counting bytes…. especially in Assembler language.Fortunately, we usually don’t need to deal in large numbers of bytes in our programs – a couple of hundred at a time, at most. Most of the time, many fewer than that – enough to fill an input or output buffer and we must accurately count the number of bytes within each field. Counting bytes seems to never end.

An older Mainframe Computer

IBM Stretch Computer - 7030

Circa 1964-1965

You can see a portion of the operator’s console on the very left side of this photo. The panels that open contain circuitry of the processor and memory.

Here is a look inside one of those panels that opens. How would you like to be the person who must do repairs on this computer?This is, of course, in the days before integrated circuitry. It was all hand-wired and (by today’s standard) very slow, although this was the faster computer in existence in its day. This is the computer that the first man-on-the-moon satellite was programmed.

Today’s Mainframe – Z/10

1 – 64 4.4GHz processors

1.52 Terabytes memory

6 ft. tall with a 30 Sq. Ft. footprint

2.5 tons

Computer power of 1500 industry-standard servers using 85% less power and covering 85% less floor space. Not much to look at, is it?

Announced Feb. 2008

A mainframe processor consists of …

• A Control Unit– Fetches instructions

• An Arithmetic and Logic Unit– Performs arithmetic– Compares

• General Purpose Registers• Just like a PC

And How Fast ???

Small z/9 system

Large z/9 system

Parallel systems up to 32

Pentium4E

(2004)

26MIPS

17,801MIPS

221,248MIPS

3.2GHz

Max11,000MIPS

MIPS stands for Millions of Instructions Per Second – and represents the measurement for mainframe speed (similar to PC GHz). It is a measurement that is no more accurate that GHz and has earned the new acronym meaning of Meaningless Indicator of Processor Speed.

Memory

• Capacity– PC --- 4 GB ?– Mainframe --- 1.52 TB ?

• Simultaneous Users– PC --- a few– Mainframe --- hundreds of thousands

Storage Devices

• Disk• Tape• CD• DVD• Flash Drive• paper

2 GB Flash Drive

9 MB Write / 15 MB Read

Retractable USB Connect

About $110

Magnetic Disk (PC)

TrackSector

Track

Magnetic Disk (PC)

Filename0

Filename1

Filename2

Filename3

Filename4

-

-

-

FATDirectory

Disk (Mainframe)

Catalog

pp. 22 & 23

VolumeFilename1 Vol label

Filename2 Vol label

Filename3 Vol label

Filename4 Vol label

filename5 Vol label

-

-

-

Catalog

Filename1

Filename2

VTOCVTOC = Volume Table of Contents

All files are typically cataloged and are usually found by using the catalog. Catalog entry points to the volume and VTOC that contains the file. Other routines verify that the file is really there.

Volume Table of Contents

Filename-1 DSCB

Filename-n DSCB

So how is the file found? Look in the catalog to find the volume, then look in the VTOC on the volume that contains the file. The DSCB is essentially a list of files (by name) located on the volume and its beginning cylinder and track number. Remember, the access arm on the device must be moved and that’s a mechanical (take-forever) process compared to memory speeds.

5.25”

19.0”

Another Mainframe deviceDS6800 from IBM

Capacity: up to 64 TBTransfer Rate: up to 1600 MB per sec.16 disk units (max: 128 units)

Accessing Data

• OPEN / CLOSE macros• OPEN prior to first access to data• CLOSE after last access to data,

usually in your eof routine

[label] OPEN dcb-label

[label] CLOSE dcb-label

Accessing Data

• Data Control Block (DCB)

• LRECL = length of record in bytes• RECFM = F for fixed-length• MACRF = G/P for Get/Put• DDNAME = path and filename• EODAD = input-only (label for EOF rtn.)

dcb-label DCB operand1,operand2,..

INDCB DCB LRECL=80,RECFM=F,MACRF=G,EODAD=EOFRTN,DDNAME=F:\TIMECDS.TXT

MVZ TOTAL+6(1),FCHAR replace the C with F for printing BR 5 return to main process ****************************************************************************** * END OF PROCESSING ****************************************************************************** DONE CLOSE LISTINGS close listings.txt file CLOSE REALTORS close realtors.txt file CLOSE CUSTOMER close customer.txt file CLOSE OUTPUT close output.txt file RETURN ****************************************************************************** *DECLARATIVES* ****************************************************************************** LISTINGS DCB LRECL=101,RECFM=F,MACRF=G,EODAD=LOOP02,DDNAME='h:\LISTINGS.TXT' REALTORS DCB LRECL=101,RECFM=F,MACRF=G,EODAD=HEADING,DDNAME='h:\REALTORS.TXT' CUSTOMER DCB LRECL=101,RECFM=F,MACRF=G,EODAD=DONE,DDNAME='h:\CUSTOMER.TXT' OUTPUT DCB LRECL=101,RECFM=F,MACRF=P,DDNAME='h:\OUTPUT.TXT' ******************************************************************************

Example (from REALTORS)

No need to test for EOF. Provide EODAD= rtn and the system will automatically take the branch when EOF occurs.

Accessing Data

• GET / PUT a Record• Input or Output 1 logical record

[label] GET dcb-label,area-name

[label] PUT dcb-label,area-name

OPEN INDCBOPEN OUTDCBGET INDCB,INBUFFPUT OUTDCB,OUTBUFFCLOSE INDCBCLOSE OUTDCB

START 0 *** *** OPEN LISTINGS open input file to be printed OPEN OUTPUT open or create output.txt file LOOP GET LISTINGS,LINE get line from input.txt file PUT OUTPUT,LINE put line to output.txt file B LOOP repeat ****************************************************************************** * END OF PROCESSING ****************************************************************************** DONE CLOSE LISTINGS close listings.txt file CLOSE OUTPUT close output.txt file RETURN ****************************************************************************** *DECLARATIVES* ****************************************************************************** LISTINGS DCB LRECL=101,RECFM=F,MACRF=G,EODAD=DONE,DDNAME='h:\LISTINGS.TXT' OUTPUT DCB LRECL=101,RECFM=F,MACRF=P,DDNAME='h:\OUTPUT.TXT' ****************************************************************************** LINE DS CL101 101 character line *** END START END PROCESS TITLED 'START'

Snippet of Code

End of I/O Slide Show