Input and Output

This lesson covers input and output operations as required by OCR J277 Section 2.3. Input and output (often abbreviated as I/O) are fundamental to every program — without them, a program cannot receive data from the user or display results.

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What Is Input?

Input is data entered into a program by the user or received from another source (such as a file or sensor). In OCR GCSE Computer Science, input typically means data entered via the keyboard.

OCR Pseudocode:

name = input("What is your name? ")
age = int(input("How old are you? "))

Python:

name = input("What is your name? ")
age = int(input("How old are you? "))

Important Points About Input

Point	Explanation
input() always returns a string	Even if the user types 42, it is stored as the string "42"
You must cast for numbers	Use int() for integers, float() (or real() in OCR pseudocode) for decimals
The prompt message is optional	But it is good practice to tell the user what to enter
Input waits for the user	The program pauses until the user presses Enter

OCR Exam Tip: If the exam question says "the user enters a number", you must use int(input()) or real(input()). Forgetting to cast is a common mistake that means arithmetic operations would fail or give unexpected results.

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What Is Output?

Output is data displayed by the program, typically on the screen. In OCR pseudocode and Python, the print() function is used for output.

OCR Pseudocode:

print("Hello, world!")
name = "Alice"
print("Welcome, " + name)
score = 95
print("Your score is: " + str(score))

Python:

print("Hello, world!")
name = "Alice"
print("Welcome, " + name)
score = 95
print("Your score is:", score)  # Python's print() can accept multiple arguments
print("Your score is: " + str(score))  # String concatenation version

Formatting Output

When combining text and numbers in output, you often need to convert numbers to strings:

OCR Pseudocode:

price = 9.99
quantity = 3
total = price * quantity
print("Total: £" + str(total))

Python:

price = 9.99
quantity = 3
total = price * quantity
print("Total: £" + str(total))
# Or using f-strings (more modern Python):
print(f"Total: £{total}")
# Or using format to 2 decimal places:
print(f"Total: £{total:.2f}")

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Combining Input and Output

A typical program follows an Input → Process → Output pattern:

OCR Pseudocode:

// Input
length = real(input("Enter length: "))
width = real(input("Enter width: "))

// Process
area = length * width

// Output
print("The area is: " + str(area))

Python:

# Input
length = float(input("Enter length: "))
width = float(input("Enter width: "))

# Process
area = length * width