Turning Learners into Developers
- All C Keywords – One Complete & Understandable Table
Keyword | C Standard | Easy Description | Example / Usage |
|---|---|---|---|
auto | C90 | Default local variable inside a function | auto int x = 10; |
break | C90 | Immediately stops loop or switch | if(i==5) break; |
case | C90 | A matching option in switch | case 1: printf("One"); |
char | C90 | Stores a single character | char ch = 'A'; |
const | C90 | Value cannot be changed | const int x = 10; |
continue | C90 | Skips current loop step | if(i==3) continue; |
default | C90 | Runs if no case matches | default: printf("Invalid"); |
do | C90 | Loop runs at least once | do{ i++; }while(i<5); |
double |
| Stores large decimal values | double d = 5.25; |
else | C90 | Runs when | else printf("No"); |
enum |
| Creates named integer constants | enum Day {MON,TUE}; |
extern | C90 | Uses global variable from another file | extern int x; |
float | C90 | Stores decimal numbers | float f = 3.14; |
for | C90 | Loop with initialization and counter | for(i=0;i<5;i++) |
goto | C90 | Jumps to a labeled statement | goto label; |
if | C90 | Executes when condition is true | if(x>0) |
int | C90 | Stores whole numbers | int a = 10; |
long |
| Stores larger integers | long int x; |
register | C90 | Suggests faster memory access | register int i; |
return | C90 | Sends value back from function | return 0; |
short |
| Stores smaller integers | short int s; |
signed | C90 | Allows positive and negative values | signed int x; |
sizeof |
| Finds size of variable/type | sizeof(int) |
static |
| Retains value between function calls | static int count; |
struct | C90 | Groups different data types | struct Student {int id;}; |
switch | C90 | Multiple condition selection | switch(choice) |
typedef |
| Creates new name for data type | typedef int INT; |
union | C90 | Shares memory for all members | union Data {int i;}; |
unsigned |
| Stores only positive values | unsigned int x; |
void | C90 | No value or return type | void show() |
volatile |
| Value can change anytime | volatile int flag; |
while |
| Loop runs while condition is true | while(i<5) |
inline |
| Suggests faster function execution | inline int add() |
_Bool | C99 | Stores true or false | _Bool flag = 1; |
_Complex | C99 | Stores complex numbers | _Complex float z; |
_Imaginary | C99 | Stores imaginary numbers | _Imaginary float y; |
restrict |
| Improves pointer performance | int *restrict p; |
_Alignas | C11 | Sets memory alignment | _Alignas(16) int x; |
_Alignof |
| Gets alignment size | _Alignof(int) |
_Atomic |
| Ensures safe shared access | _Atomic int count; |
_Generic |
| Selects code by data type | _Generic(x,int:1) |
_Noreturn | C11 | Function never returns | _Noreturn void exit() |
_Static_assert | C11 | Compile-time condition check | _Static_assert(1,"OK"); |
_Thread_local | C11 | Separate variable for each thread | _Thread_local int x; |
- Key Exam Notes
- 32 keywords in standard C (C90)
- C99 adds 5 keywords
- C11 adds 7 keywords
- Keywords are lowercase & reserved
- Cannot be used as identifiers
