Chapter 3

Variables

Variables in C are declared differently than in Pascal. The format for variable declarations in C is:

 <type> <identifier>;

So the following would declare an integer variable named "x".

 int x;

C allows multiple variables to be declared on the same line.

 int x, y, z;  /* declare x, y, and z */

C also allows a value to be assigned to the variable when it is declared. Unlike Pascal, the C assignment statement is "=" instead of ":="

int x = 10;    /*assign 10 to x */

The following program shows examples of how variables can be used. Please note that the comments explain how the program works

#include <stdio.h>

int a, x;
float y;
char z;

void main(void) {
  
  x = 1;   /* assign 1 to x */
  printf(" %d \n", x);

  y = 2.5;
  printf(" %f \n", y);  /* assign 2.5 to y */

  z = 'R';            
  printf(" %c \n", z);

  a = x;
  printf(" %d \n", a);

  a = 2 * x;
  printf(" %d \n", a);

}

Data Types

C defines several datatypes these are the most common.

int	Integer - holds whole numbers from -32,768 to 32,767
float	Floating point - holds numbers with digits after the decimal
double	Double Precision floating point - same as float but with greateer precision
char	Character - holds single ASCII characters.

Math Operators

Addition

x = 2 + 2;

Subtraction

x = 2 - 1;

Multiplication

x = 2 * 4

Division

x = 4 / 2;

Modulus (remainder)

x = 5 % 2;

Other math operators.

The following make common operations faster.

Addition "++"

 i++;   /* increment i by one */

Subtraction "--"

i--;   /* decrement i by one */

Addition "+="

 i += 10;  /* same as i = 1 + 10;

Subtraction "-="

 i -= 10; /*same as i = 1 - 10

Multiplication "*="

 i *= 10;    /*  same as i = i * 10;  */

Division "/="