Types, Operators and Expressions

Types, Operators and Expressions
Data Types

C provides the following basic data types: char, int, float and double.
In addition, there are a few qualifiers which can be applied to int: short, long and unsigned.
In C, all variables must be declared before they are used.
The following code, which prints a conversion chart, demonstrates the use of several C data types.

//****************************************************************************************************

//* Title: conversion.c Author: N. Bercich

//*

//* This program prints a chart showing the conversion of miles to kilometers for

//* every five miles between 0 and 200.

//****************************************************************************************************

#include <stdio.h>

main()

{

int miles=0, step=5, max=200;

float kilometers=0;

for (miles=0; miles <= max; miles=miles+step)

{

kilometers = miles * 1.61;

printf("%d miles is %3.2f kilometers\n", miles, kilometers);

}

Variations on the basic int data type exist, including short, long and unsigned.
For more detail on each of these basic data types, please check a standard C documentation guide.
C allows you to define both character and numeric constants. Again, for detailed specifications, check a standard C documentation guide.

Operators

C provides the following binary operators: +, -, *, / and %.
The modulus operator, %, cannot be applied to float or double.
There is a unary – as well as the increment and decrement operators, ++ and --.
The relational operators, >, >=. <. <=. != and == are also provided.
C follows the standard rules for arithmetic precedence.
( and ) are provided to allow normal precedence to be overridden.
If you are unfamiliar with these rules, again, check a standard C documentation guide.

Data Conversion

When operands of different types appear in an expression, they are converted to a common type.
As a rule, only conversions that make sense happen automatically.
Nonsensical expressions are, typically, disallowed.
For example, in the above program, miles is automatically converted to float before it is multiplied by 1.61.
The C libraries include functions for making "other" conversions. One example is the function atoi(s) which converts a string of digits to a decimal value.
To learn more about the atoi(s) function, and other similar functions, use the man command on the UNIX box. Enter, man atoi, after the prompt.

Exercises