C Programming Functions and String Manipulation

Input Functions

• getc() reads a character from the standard input (usually the keyboard) and returns it as an integer.
• getchar() is a macro that calls getc() with stdin as the argument, making it equivalent to getc(stdin).
• getch() is a non-standard function that reads a character from the standard input without echoing it to the console.
• getche() is a non-standard function that reads a character from the standard input and echoes it to the console.

Random Number Generation

• rand() generates a random integer between 0 and RAND_MAX (a constant defined in ``).
• srand() seeds the random number generator with an initial value, allowing rand() to produce a sequence of random numbers.

Character Classification

• isupper() returns a non-zero value if the character is an uppercase letter.
• islower() returns a non-zero value if the character is a lowercase letter.

String Manipulation

strcpy()

• Copies the string pointed to by the second argument into the array pointed to by the first argument.
• Returns a pointer to the destination array.
• Example: strcpy(dest, "hello"); copies the string "hello" into the array dest.

strcat()

• Appends the string pointed to by the second argument to the end of the string pointed to by the first argument.
• Returns a pointer to the destination array.
• Example: strcat(dest, "world"); appends the string "world" to the end of the string in dest.

strlen()

• Returns the length of the string pointed to by the argument.
• Example: strlen("hello"); returns 5.

strcmp()

• Compares the string pointed to by the first argument to the string pointed to by the second argument.
• Returns an integer indicating the result of the comparison: 0 if the strings are equal, less than 0 if the first string is less than the second, greater than 0 if the first string is greater than the second.
• Example: strcmp("hello", "goodbye"); returns a value indicating that "hello" is less than "goodbye".

Command Line Argument Conversion

• To convert a command line argument from a string to an integer, use the atoi() function from ``.
• Example: int arg = atoi(argv[1]); converts the first command line argument to an integer.

This quiz covers the differences and usage of various C programming functions such as getc, getchar, getch, getche, rand, srand, isupper, islower, strcpy, strcat, strlen, and strcmp. It also includes converting command line arguments to integers.