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Ultimate C Programming Reference

Ultimate C Programming Reference





⚡ ULTIMATE C PROGRAMMING REFERENCE ⚡

Your complete guide to C programming mastery





Functions
Memory
Strings
Math
Files
Glossary




🔥 BASIC I/O FUNCTIONS




Function

Description

Example





printf()
print formatted output to screen
printf("hello %s\n", name);


scanf()
read formatted input from user
scanf("%d", &number);


getchar()
read single character
char c = getchar();


putchar()
print single character
putchar('A');


puts()
print string with newline
puts("hello world");


fgets()
safe string input
fgets(buffer, 100, stdin);








💾 MEMORY MANAGEMENT




Function

Description

Example





malloc()
allocate memory on heap
int *ptr = malloc(10 * sizeof(int));


calloc()
allocate zeroed memory
int *ptr = calloc(10, sizeof(int));


realloc()
resize allocated memory
ptr = realloc(ptr, 20 * sizeof(int));


free()
deallocate memory
free(ptr);


sizeof()
get size of data type
int size = sizeof(int);








📝 STRING FUNCTIONS

Requires: #include <string.h>




Function

Description

Example





strlen()
get string length
int len = strlen("hello");


strcpy()
copy string
strcpy(dest, source);


strncpy()
copy n characters
strncpy(dest, source, 5);


strcat()
concatenate strings
strcat(dest, source);


strcmp()
compare strings
if (strcmp(str1, str2) == 0)


strchr()
find character in string
char *pos = strchr(str, 'a');


strstr()
find substring
char *pos = strstr(str, "hello");








🧮 MATH FUNCTIONS

Requires: #include <math.h>




Function

Description

Example





pow()
power function
double result = pow(2.0, 3.0);


sqrt()
square root
double result = sqrt(16.0);


abs()
absolute value (int)
int result = abs(-5);


fabs()
absolute value (double)
double result = fabs(-5.5);


ceil()
round up
double result = ceil(4.2);


floor()
round down
double result = floor(4.8);


rand()
random number
int num = rand() % 100;


srand()
seed random generator
srand(time(NULL));








📁 FILE OPERATIONS




Function

Description

Example





fopen()
open file
FILE *fp = fopen("file.txt", "r");


fclose()
close file
fclose(fp);


fread()
read from file
fread(buffer, 1, 100, fp);


fwrite()
write to file
fwrite(data, 1, 100, fp);


fprintf()
print to file
fprintf(fp, "number: %d\n", num);


fscanf()
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