A Quick Reference to C Programming Language

Structure of a C Program

#include(stdio.h) /* include IO library */
#include... /* include other files */
#define.. /* define constants */
/* Declare global variables*/)
(variable type)(variable list);
/* Define program functions */
(type returned)(function name)(parameter list)
(declaration of parameter types)
{
(declaration of local variables);
(body of function code);
}
/* Define main function*/ main ((optional argc and argv arguments))
(optional declaration parameters)
{
(declaration of local variables);
(body of main function code);
}

Comments
Format: /*(body of comment) */
Example: /*This is a comment in C*/

Constant Declarations
Format: #define(constant name)(constant value)
Example: #define MAXIMUM 1000

Type Definitions
Format: typedef(datatype)(symbolic name);
Example: typedef int KILOGRAMS;

Variables
Declarations:
Format: (variable type)(name 1)(name 2),...;
Example: int firstnum, secondnum; char alpha; int firstarray[10]; int doublearray[2][5]; char firststring[1O];

Initializing:
Format: (variable type)(name)=(value);
Example: int firstnum=5;
Assignments:
Format: (name)=(value);
Example: firstnum=5;
Alpha='a';

Unions
Declarations:
Format: union(tag)
{(type)(member name);
(type)(member name);
...
}(variable name);
Example: union demotagname
{int a; float b;
}demovarname;
Assignment:
Format: (tag).(member name)=(value); demovarname.a=1; demovarname.b=4.6;

Structures
Declarations:
Format: struct(tag)
{(type)(variable);
(type)(variable);
...
}(variable list);
Example: struct student
{int idnum; int finalgrade; char lettergrade;
} first,second,third;
Assignment:
Format: (variable name).(member)=(value);
Example: first.idnum=333; second.finalgrade=92; Operators
Symbol Operation Example
+,-,*,/ arithmetic 1 = b + c;
% mod a = b % c;
> greater than if (a > b)
>= greater than or equal if (a >= b)
< less than if (a > 2;