C – Program Code – Basics Part III

Precedence of Evaluation of expression

→

()

When parenthesis are nested, innermost parenthesis first evaluated.

Implicit Type conversation

Automatic conversion of variables and constants of different types in an expression to proper type.

Conversion Hierarchy

Explicit conversion

(type-name) expression

e.g. x = (int)(y+0.8)

C Operator Precedence Table

This page lists C operators in order of precedence (highest to lowest). Their associativity indicates in what order operators of equal precedence in an expression are applied.

Operator	Description	Associativity
( ) [ ] . -> ++ --	Parentheses (function call) (see Note 1) Brackets (array subscript) Member selection via object name Member selection via pointer Postfix increment/decrement (see Note 2)	left-to-right
++ -- + - ! ~ (type) * & sizeof	Prefix increment/decrement Unary plus/minus Logical negation/bitwise complement Cast (convert value to temporary value of type) Dereference Address (of operand) Determine size in bytes on this implementation	right-to-left
* / %	Multiplication/division/modulus	left-to-right
+ -	Addition/subtraction	left-to-right
<< >>	Bitwise shift left, Bitwise shift right	left-to-right
< <= > >=	Relational less than/less than or equal to Relational greater than/greater than or equal to	left-to-right
== !=	Relational is equal to/is not equal to	left-to-right
&	Bitwise AND	left-to-right
^	Bitwise exclusive OR	left-to-right
\|	Bitwise inclusive OR	left-to-right
&&	Logical AND	left-to-right
\| \|	Logical OR	left-to-right
? :	Ternary conditional	right-to-left
= += -= *= /= %= &= ^= \|= <<= >>=	Assignment Addition/subtraction assignment Multiplication/division assignment Modulus/bitwise AND assignment Bitwise exclusive/inclusive OR assignment Bitwise shift left/right assignment	right-to-left
,	Comma (separate expressions)	left-to-right
Note 1: Parentheses are also used to group sub-expressions to force a different precedence; such parenthetical expressions can be nested and are evaluated from inner to outer. Note 2: Postfix increment/decrement have high precedence, but the actual increment or decrement of the operand is delayed (to be accomplished sometime before the statement completes execution). So in the statement *y = x z++;** the current value of z is used to evaluate the expression (i.e., z++ evaluates to z) and z only incremented after all else is done.
Source : http://www.difranco.net/

Reading a character

variable_name = getchar();

e.g.

printf(“Type (Y/N) :”);
answer = getchar();

getchar() function accepts any character keyed in, including RETURN / ENTER and TAB.
Character test functions:
isalnum(c), isalpha(c), isdigit(c), islower(c), isprint(c), ispunct(c), isspace(c), isupper(c)
Writing a character

putchar(variable_name);

e.g. answer = ‘y’;

putchar(answer);

Reading formatted input

scanf(“control string”, arg1, arg2, … argn);
e.g. scanf(“%2d %5d”, &num1, &num2);

Reading character strings using specified character width (number of characters)

%ws or %wc

e.g.
scanf(“%d %15c”, &no, name1);

%s specifier can’t be used to read strings with blank spaces. But, blank spaces can be read using %[] specification.
Scanf format codes / Applicable to printf statements also.

Format	To read
%c	Single character
%d	Decimal integer
%e	Floating point value
%f	Floating point value
%g	Floating point value (either e type or f type)
%h	Short integer
%i	Decimal / hexadecimal or Octal Integer
%o	Octal integer
%s	String
%u	Unsigned decimal integer
%x	Read a hexadecimal integer
%[..]	String of words

Prefix:

h – for short integers

l – for long integers or double

L – for long double

Important points to remember while using scanf:

All function arguments except the control string (s) must be pointers to variables.
Control string format specification should match with arguments order
Input data items separated by spaces in the same order