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CheatSheet

C Programming

1 KEYWORDS (these words are reserved for the language and cannot be used as any variable name by the user)

auto double int struct break else long switch case enum register typedef char extern return union const float short unsigned continue for signed void default goto sizeof volatile do if static while

2 ALLOWED CHARACTER SET

Alphabets - A, B, ….., Y, Z a, b, ……, y, z
Digits - 0, 1, 2, 3, 4, 5, 6, 7, 8, 9
Special symbols - ~ ‘ ! @ # % ^ & * ( ) _ - + = | \ { } [ ] : ; " ' < > , . ? /

3 DATA TYPES and PLACEHOLDERS

Some common datatypes are:

int - integer
char - character
long - long integer
float - float number
double - long float

use scanf to take input from the user scanf("Format string",&variable,&variable,...);

Placeholders Format
%c Character
%d Signed decimal integer
%i Signed decimal integer
%e Scientific notation[e]
%E Scientific notation[E]
%f Decimal floating point
%o unsigned octal
%s String of character
%u unsigned decimal integer
%x unsigned Hexadecimal (lower)
%X unsigned Hexadecimal (upper)
%p dispaly a pointer
%% print a %

ESCAPE SEQUENCES

\a - Bell \n - New line \r - Carriage return \b - Backspace \f - Formfeed \t - Horizontal tab " - Quotation mark \v - Vertical tab ' - Apostrophe \ - Backslash ? - Question mark \0 - Null

5 PRECEDENCE ORDER

DESCRIPTION OPERATORS ASSOCIATIVITY
Function Expression () Left to Right
Array Expression [] Left to Right
Structure Operator -> Left to Right
Structure Operator . Left to Right
Unary minus - Right to Left
Increment/Decrement ++, -- Right to Left
One’s compliment ~ Right to Left
Negation ! Right to Left
Address of & Right to Left
Value of address * Right to Left
Type cast (type) Right to Left
Size in bytes sizeof Right to Left
Multiplication * Left to Right
Division / Left to Right
Modulus % Left to Right
Addition + Left to Right
Subtraction - Left to Right
Left shift << Left to Right
Right shift >> Left to Right
Less than < Left to Right
Less than or equal to <= Left to Right
Greater than > Left to Right
Greater than or equal to >= Left to Right
Equal to == Left to Right
Not equal to != Left to Right
Bitwise AND & Left to Right
Bitwise exclusive OR ^ Left to Right
Bitwise inclusive OR
Logical AND && Left to Right
Logical OR
Conditional ?: Right to Left
Assignment =, *=, /=, %=, +=, -=, &=, ^=, =, <<=, >>=
Comma , Right to Left

6 IF-ELSE STATEMENT

if(flag) {
   // put some statements here to execute if flag is true (flag != 0)
} 
else if(flag) {
   // put some statements here to execute if flag is true (flag != 0)
} else {
   // put some statements here to execute if flag is false (flag == 0)
}

7 SWITCH-CASE STATEMENT

switch(flag) {
    case 0:  // statements
   	break;
    case 1:  // statements
  	break;
    case 2:  // statements
  	break;
    default:  // statements
}

8 WHILE LOOP

//for single statement  
while(expression) 
    statement;

//for multiple statement   
while(expression) 
{ 
    block of statement 
}

9 FOR LOOP

for ( initialization; test condition; run every time command )

eg:
int i;
for (i =0;i<3;i++):
    printf("%d",&i);
will give 012 as output

10 DO-WHILE STATEMENT

do
{
    statements;
}while (expression);

11 BREAK CONTINUE STATEMENT

  • break statement is used to terminate the current loop the moves to the next line of the code.
  • continue statement skips the current loop index and moves to the next iteration.

###12 GOTO syntax of goto is as follows: goto label; .. . label: statement; example: int a = 10; /* do loop execution */ LOOP:do {

  if( a == 15) {
     /* skip the iteration */
     a = a + 1;
     goto LOOP;
  }
	
  printf("value of a: %d\n", a);
  a++;

}while( a < 20 ); will give the output to be: value of a: 10 value of a: 11 value of a: 12 value of a: 13 value of a: 14 value of a: 16 value of a: 17 value of a: 18 value of a: 19

12 ARRAYS

  1. Declaraction:

typeof_array array_name[size];

Eg:
int arr[10]; // makes an integer array of size 10
int num[6] = { 2, 4, 12, 5, 45, 5 } ; 
2)Accessing Elements:
int k=arr[2]; //k stores the element at index 2 of the array
3)Entering data:
for(i =0;i<3;i++){
  scanf("%d", &arr[i]); // takes the values in the array arr by the user
}

### 13 STRINGS

1)Declaraction:

char string_name[size]; scanf("%s",string_nam);


- A string has '\0' as the last element which tells the end of string
- It is accessed in the same way as an array
- A string is in many ways similar to array

2. Some basic built-in fucntions of strings

> Just include string.h at the top of your code

strlen - Finds length of a string strlwr - Converts a string to lowercase strupr - Converts a string to uppercase strcat - Appends one string at the end of another strncat - Appends first n characters of a string at the end of another strcpy - Copies a string into another strncpy - Copies first n characters of one string into another strcmp - Compares two strings strncmp - Compares first n characters of two strings strcmpi - Compares two strings without regard to case ("i" denotes that this function ignores case) stricmp - Compares two strings without regard to case (identical to strcmpi) strnicmp - Compares first n characters of two strings without regard to case strdup - Duplicates a string strchr - Finds first occurrence ofa given character in a string strrchr - Finds last occurrence ofa given character in a string strstr - Finds first occurrence of a given string in another string strset - Sets all characters ofstring to a given character strnset - Sets first n characters ofa string to a given character strrev - Reverses string


### 13 STRUCTURE 
	
- A structure is a user defined data type in C/C++. A structure creates a data type that can be used to group items of possibly different types into a single type. 

>‘struct’ keyword is used to create a structure. Following is an example.

struct addrress { char name[50]; char street[100]; char city[50]; char state[20]; int pin; };