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Chapter 4 Basic Data Types and Variables

4.1 Basic Data Types In C

TABLE 4.1 Introduction to Basic Data Types in C

Type Size Description

char 1 byte Characters or small integer variables

int 2 or 4 bytes Integer values

float 4 bytes Floating point numbers

double 8 bytes Floating point numbers

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4.2 CHARACTERS

The Standard for Text: ASCII(American Standard Code for Information Interchange) was first defined by the American National Standards Institute in 1986. In this code, each letter of the alphabet, punctuation mark, and decimal number is assigned a unique 7-bit code number. With 7 bits, 128 unique symbols can be coded. See Table 4.2.

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0 nul 16 dle ^P 32 48 0 64 @ 80 P 96 ` 112 p1 soh ^A 17 dcl ^Q 33 ! 49 1 65 A 81 Q 97 a 113 q2 stx ^B 18 dc2 ^R 34 " 50 2 66 B 82 R 98 b 114 r3 etx ^C 19 dc3 ^S 35 # 51 3 67 C 83 S 99 c 115 s4 eot ^D 20 dc4 ^T 36 $ 52 4 68 D 84 T 100 d 116 t5 enq ^E 21 nak ^U 37 % 53 5 69 E 85 U 101 e 117 u6 ack ^F 22 syn ^V 38 & 54 6 70 F 86 V 102 f 118 v7 bel ^G 23 etb ^W 39 ' 55 7 71 G 87 W 103 g 119 w8 bs ^H 24 can ^X 40 ( 56 8 72 H 88 X 104 h 120 x9 tab ^I 25 em ^Y 41 ) 57 9 73 I 89 Y 105 I 121 y10 lf ^J 26 eof ^Z 42 * 58 : 74 J 90 Z 106 j 122 z11 vt ^K 27 esc ^[ 43 + 59 ; 75 K 91 [ 107 k 123 {12 np ^L 28 fs ^\ 44 ' 60 < 76 L 92 \ 108 l 124 |13 cr ^M 29 gs ^] 45 - 61 = 77 M 93 ] 109 m 125 }14 so ^N 30 rs ^^ 46 . 62 > 78 N 94 ^ 110 n 126 ~15 si ^O 31 us ^_ 47 / 63 ? 79 O 95 _ 111 o 127 del

TABLE 4.2 ASCII Character Format

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4.2.1 Defining Character Variables in C

Program 4.1: C Program Containing Variables

int main ( void ) { /* Beginning of the (main) block. */

Char cAChar; /* We put variable definitions here. */

cAChar = 65 ; /* Executable statement : assign the */

/* code for ‘A’ to “cAChar” */

} /* End of (main) block */

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4.2.2 Character Constants

cAChar = ‘A’ ; /*assign ‘A’ to character */ /* variable “cAChar”

*/

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4.2.3 Escape Characters

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Remark 4.2

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4.3 INTEGERS

Consider for example the declarationsint iPennies;

int iCounter;

Initial Values can also be supplied in definitions, as with

int iCounter = 0;

int iNickels = 5;

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4.3.1 Short and Long Integersshort <= int <= long

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4.3.2 Unsigned Integers

Ex:

unsigned int uiPennies;

unsigned uUpCounter;

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4.4 SINGLE AND DOUBLE PRECISION FLOATING POINT NUMBERS

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4.4.1 Floating Point Variables

Floating point variables and constants:

3.4, -45.33, 2.714,

Exponential notation:

3.0e-25, 4.5e+05, 2.345678e+19,

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Figure 4.2

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Table 4.5

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Program 4.2 : Print size of some basic data types

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接續 Program 4.2

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4.5 ENUMERATION DATA TYPESenum weekday { Mon, Tue, Wed, Thu, Fri, Sat, Sun }; or

enum dayofweek { Mon=1, Tue, Wed, Thu, Fri, Sat, Sun };

Program 4.3

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4.6 VARIABLE ATTRIBUTES: TYPE, ADDRESS, NAME, AND VALUE

int iVal = 10;

Type Name Value

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Program 4.4

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4.7 VARIABLE NAMING CONVENTIONS

A variable name cannot start with a digit, and it cannot have the same as a reserved word.

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An appropriate name name for our count variable:

int iCount ;

unsigned int uiCount ;

unsigned uCount;

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