Lesson 6: Input/Output Statements in C

What does I/O mean in C programming?

I/O stands for Input/Output, which is the process of reading (input) and writing (output) data in a program.

Which header file contains C input/output functions?

<stdio.h> (standard input/output header file).

What are the two main classifications of I/O functions in C?

Unformatted I/O functions and Formatted I/O functions.

What are the six unformatted I/O functions?

getchar(), putchar(), gets(), puts(), getch(), getche().

What does getchar() do?

Reads a single character from the keyboard (buffered, requires Enter).

What does putchar() do?

Displays a single character on the screen.

What does gets() do?

Reads a string (until Enter is pressed) and adds a null character \0 at the end.

What does puts() do?

Outputs a string or text message, automatically appending a newline.

How does getch() differ from getchar()?

getch() reads a single character without waiting for Enter (non-buffered).

What is the difference between getch() and getche()?

Both are non-buffered, but getche() echoes (displays) the character on screen while getch() does not.

What are the two formatted I/O functions?

scanf() (input) and printf() (output).

How is scanf() used?

scanf("control string", &var1, &var2, …);

What does the & symbol mean in scanf()?

It passes the address of the variable so input can be stored there.

What are some common format specifiers for scanf()?

• %c → character

• %d → integer

• %f → float

• %lf → double

• %s → string

• %x → hexadecimal

• %o → octal

%c

character

%d

integer

%f

float

%lf

double

%s

string

%x

hexadecimal

%o

octal

How is printf() used?

printf("control string", var1, var2, …);

What are some common format specifiers for printf()?

• %c → character

• %s → string

• %d → integer

• %f → float

• %lf → double

• %x → hexadecimal

• %o → octal

%c

character

%s

string

%d

integer

%f

float

%lf

double

%x

hexadecimal

%o

octal

Which I/O functions are used for strings in unformatted I/O?

gets() and puts().

Which I/O functions are used for single characters?

getchar(), putchar(), getch(), getche().

Which I/O functions allow formatted input/output with multiple data types?

scanf() and printf().

What’s the main difference between unformatted and formatted I/O?

• Unformatted I/O → handles raw character/string input/output.

• Formatted I/O → allows structured input/output with format specifiers.

What does I/O mean in C programming?

Input/Output — reading (input) and writing (output) data in a program.

Which header file is required for I/O in C?

#include <stdio.h>

What are the two main classifications of I/O functions?

Unformatted I/O and Formatted I/O.

What is the syntax of getchar()?

char c;
c = getchar();

Reads a single character from the keyboard (buffered, requires Enter).

What is the syntax of putchar()?

char c = 'A';
putchar(c);

Displays a single character on the screen.

What is the syntax of gets()?

char str[20];
gets(str);

Reads a string (until Enter is pressed). Appends \0 at the end.

What is the syntax of puts()?

puts("Hello");
puts(str);

Outputs a string or text message and automatically adds a newline.

What is the syntax of getch()?

char c;
c = getch();

Reads a single character (non-buffered, no Enter needed). Character is not displayed.

What is the syntax of getche()?

char c;
c = getche();

Reads a single character (non-buffered) and echoes it on the screen.

What is the syntax of scanf()?

scanf("format_specifiers", &var1, &var2, ...);

Reads input in a specific format.

Example of scanf

int age;
float gpa;
scanf("%d %f", &age, &gpa);

What is the syntax of printf()?

printf("format_specifiers", var1, var2, ...);

Displays output in a formatted way.

Example of printf

int age = 20;
float gpa = 1.75;
printf("Age: %d, GPA: %.2f", age, gpa);

Unformatted Input

getchar(), gets(), getch(), getche()

Unformatted Output

putchar(), puts()

Formatted Input

scanf()

Formatted Output

printf()