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ClanguageCheatSheet.md

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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

  1. 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 - ~ ‘ ! @ # % ^ & * ( ) _ - + = | \ { } [ ] : ; " ' < > , . ? /
  1. 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 display a pointer
%% print a %
  1. 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

  1. 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 complement ~ 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
  1. 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)
}
  1. Switch-case Statement
switch(flag) {
    case 0:  // statements
   	break;
    case 1:  // statements
  	break;
    case 2:  // statements
  	break;
    default:  // statements
}
  1. While loop
//for single statement
while(expression)
    statement;

//for multiple statement
while(expression)
{
    block of statement
}
  1. 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
  1. Do-while Statement
do
{
    statements;
}while (expression);
  1. break & continue
  • 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.

  1. 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

  1. Arrays
  • 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 } ;

  • Accessing Array elements: int k=arr[2]; //k stores the element at index 2 of the array

  • Entering data into an Array:

for(i =0;i<3;i++){
  scanf("%d", &arr[i]); // takes the values in the array arr by the user
}
  1. Strings
  • Declaration:
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

  • Some basic built-in functions 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 of a given character in a string
strrchr - Finds last occurrence of a 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 of a string to a given character
strrev - Reverses string
  1. Structures
  • 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 address
{
   char name[50];
   char street[100];
   char city[50];
   char state[20];
   int pin;
};
  • Types of structure:
    • Tagged structure - tag after struct
    • Variable structure - identifier before last semicolon
    • Type definition structure - a typedef before struct and a type identifier before last semicolon
  1. Macros
  • A macro is a single instruction that expands automatically into a set of instructions to perform a particular task.
  • Commonly used keyword are #define, #undef
  • Types of macro:
    • Simple macro
      • Macro with no variables, usually used as constants
    • Parameterized macro
      • Macro with variables, according to gcc.gnu.org: When the macro is expanded, each use of a parameter in its body is replaced by the tokens of the corresponding argument.
  1. Videos