C basic libraries- cheatsheet

basic libraries

• C <stdio.h>
• C <stdlib.h>
• C <string.h>
• C <math.h>
• C <ctype.h>

cheatsheet

stdio.h (Standard Input/Output)

1. printf - Prints formatted output to the console.
2. scanf - Reads formatted input from the console.
3. putchar - Writes a single character to the console.
4. getchar - Reads a single character from the console.
5. fopen - Opens a file.
6. fclose - Closes an open file.
7. fprintf - Writes formatted output to a file.
8. fscanf - Reads formatted input from a file.
9. fgets - Reads a string from a file or the console.
10. fputs - Writes a string to a file or the console.
11. fread - Reads binary data from a file.
12. fwrite - Writes binary data to a file.
13. feof - Checks if the end of a file has been reached.

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stdlib.h (Standard Library Utilities)

1. malloc - Allocates memory dynamically.
2. calloc - Allocates and zeroes out memory dynamically.
3. realloc - Resizes previously allocated memory.
4. free - Frees dynamically allocated memory.
5. atoi - Converts a string to an integer.
6. atof - Converts a string to a float.
7. strtol - Converts a string to a long integer.
8. rand - Generates a pseudo-random number.
9. srand - Seeds the random number generator.
10. exit - Terminates the program.
11. qsort - Sorts an array.
12. bsearch - Searches for an element in a sorted array.

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string.h (String Manipulation)

1. strcpy - Copies a string.
2. strncpy - Copies a string with a size limit.
3. strcat - Concatenates two strings.
4. strncat - Concatenates two strings with a size limit.
5. strlen - Calculates the length of a string.
6. strcmp - Compares two strings.
7. strncmp - Compares two strings with a size limit.
8. strchr - Finds the first occurrence of a character in a string.
9. strrchr - Finds the last occurrence of a character in a string.
10. strstr - Finds the first occurrence of a substring.
11. strtok - Splits a string into tokens using a delimiter.
12. memcpy - Copies a block of memory.
13. memset - Fills a block of memory with a specified value.

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math.h (Mathematical Functions)

1. sqrt - Calculates the square root of a number.
2. pow - Raises a number to a power.
3. sin - Calculates the sine of an angle (in radians).
4. cos - Calculates the cosine of an angle (in radians).
5. tan - Calculates the tangent of an angle (in radians).
6. log - Calculates the natural logarithm (base e).
7. log10 - Calculates the base-10 logarithm.
8. exp - Calculates the exponential function exe^x.
9. ceil - Rounds a number up to the nearest integer.
10. floor - Rounds a number down to the nearest integer.
11. fabs - Calculates the absolute value of a floating-point number.
12. fmod - Calculates the remainder of division.
13. hypot - Calculates the hypotenuse of a right triangle (x2+y2\sqrt{x^2 + y^2}).

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ctype.h (Character Classification and Conversion)

1. isalpha - Checks if a character is an alphabetic letter.
2. isdigit - Checks if a character is a digit (0–9).
3. isalnum - Checks if a character is alphanumeric (letter or digit).
4. isspace - Checks if a character is a whitespace character (e.g., space, tab).
5. isupper - Checks if a character is an uppercase letter.
6. islower - Checks if a character is a lowercase letter.
7. toupper - Converts a character to uppercase.
8. tolower - Converts a character to lowercase.
9. ispunct - Checks if a character is a punctuation symbol.
10. isprint - Checks if a character is printable.

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