Pseudo-Code In C

Pseudo code is a step-by-step description of an algorithm using simple English. Programmers use it to easily design, review, and refine logic before writing the actual code.

Errors are easier and cheaper to fix at this stage. Once finalized, pseudo code can be converted into different programming languages.

In this tutorial, you’ll learn different ways to write and use pseudo code in C, with simple examples for easy understanding.

Improve your C programming skills with our Software Development courses — take the next step in your learning journey!

What is Pseudo Code in C

In C programming, following syntax rules is necessary for correct execution. However, understanding complex program logic can be challenging.

Writing pseudo code first helps break down the logic in a simple way. It uses plain English, making it easier to understand.

Pseudo code represents programming logic without using a specific programming language or strict syntax. Common programming features like loops, conditionals, and function calls are written in a clear, simplified format.

Keep in mind that pseudo code cannot be compiled or executed. It is meant for humans, not computers. Since it doesn’t follow programming syntax, both programmers and non-programmers can easily understand it.

Let’s understand pseudo code with the following example:

Pseudo code:

1. Start

2. Set x = 3

3. Declare i

4. Repeat the following steps from 1 to x:

Print "Welcome!"

5. End

This pseudo code clearly explains the logic of the C program before writing actual code.

C Program:

#include <stdio.h>
int main() {
int x = 3; // Declare and assign value to x
int i; // Declare i
// Loop from 1 to x
for(i = 1; i <= x; i++) {
printf("Welcome!\n"); // Print "Welcome!" x times
}
return 0;
}

Output:

Welcome!Welcome!Welcome!

Also Read: Top 25+ C Programming Projects for Beginners and Professionals

Now that you understand what pseudo code is, you can learn how to write it effectively in C.

How to Write Pseudo Code in C

The IEEE 610.12 standard defines pseudo code as a high-level description of a program’s logic, and it emphasizes that pseudo code should be easily translatable into a specific programming language.

Effective pseudo code helps clarify program logic before coding, ensuring smoother implementation. By structuring your pseudo code properly, you make it easier to understand and convert into C code.

You can follow these guidelines to write pseudo code:

• Start with a Clear Objective → Define the purpose of the program.
• Use Simple Language → Avoid technical terms to keep it understandable.
• Break It Down → Write step-by-step instructions, each performing one action.
• Use Standard Programming Structures → Include common logic like if-else, for, and while.
• Be Consistent → Indent properly to show structure, just like in coding.
• Avoid Too Much Detail → Focus on logic, not specific syntax.
• Explain When Needed → Add comments for clarity.
• One Statement per Line → Improves readability.
• Use Capitalized Keywords → For example, START, END, IF, WHILE.
• End Multi-Line Blocks → Use ENDIF, ENDWHILE, etc., for clarity.

Pseudo code example:

START
DECLARE num1, num2, num3, average as float
INPUT num1, num2, num3
SET average = (num1 + num2 + num3) / 3
PRINT average
END

Equivalent C Code:

#include <stdio.h>
int main() {
float num1, num2, num3, average;
printf("Enter three numbers: ");
scanf("%f %f %f", &num1, &num2, &num3);
average = (num1 + num2 + num3) / 3;
printf("The average is: %.2f", average);
return 0;
}

Output Example:

Enter three numbers: 5 6 7 The average is: 6.00

Also Read: Difference Between C and Java: Which One Should You Learn?

While writing pseudo code is flexible, following certain best practices ensures clarity and consistency. Here are some key do’s and don’ts to keep in mind.

Do’s and Don’ts of Pseudo Code

Writing pseudo code effectively requires clarity, structure, and consistency. Follow these do’s and don’ts to ensure your pseudo code is useful and easy to understand.

Also Read: Command Line Arguments in C Explained

With these guidelines in place, let’s look at some practical examples to see how pseudo code is structured and used in real scenarios.

Pseudo Code Examples

These pseudo code examples will help you understand how to write pseudo code for your program.

Pseudo Code Example 1: Check if a Student Passed or Failed

IF marks >= 40
PRINT "Passed"
ELSE
PRINT "Failed"
ENDIF

Explanation: The program checks if the student's marks are 40 or more. If the marks are 40 or higher, it prints "Passed".

If the marks are less than 40, it prints "Failed". This ensures a simple way to determine if the student has met the passing criteria.

Pseudo Code Example 2: Check if a Number is Even or Odd

INPUT num
IF num % 2 == 0
PRINT "The number is even"
ELSE
PRINT "The number is odd"
ENDIF

Explanation: The program first asks the user to enter a number. It then checks if the number is divisible by 2 using the % operator. If the remainder is 0, it prints "The number is even".

Otherwise, it prints "The number is odd". This helps determine whether the number is even or odd in a simple way.

Pseudo Code Example 3: Factorial of a Number (Recursive)

FUNCTION factorial(n)
IF n == 0 THEN
RETURN 1
ELSE
RETURN n * factorial(n - 1)
ENDIF
END FUNCTION

Explanation: This recursive pseudo code calculates the factorial of a given number n. If n is 0, it returns 1 (base case). Otherwise, it recursively multiplies n by the factorial of n-1.

These simple pseudo code examples show how pseudo code breaks down logic step by step before writing the actual program.

Also Read: What Are Storage Classes in C?

Now that you’ve seen basic examples, let’s take it a step further by converting pseudo code into C programs and understanding how it translates into actual code.

Pseudo Code in C Compiler (Examples)

Pseudo code helps us understand the logic of a program before writing actual C code. Below are examples demonstrating how to convert pseudo code into C programs.

Let’s consider a program for calculating the factorial of a number:

Example 1: Factorial of a Number

Algorithm:

1. Start

2. Ask the user for input (n)

3. Check if n is negative

• If yes, print an error message and exit.
• If not, continue to step 4.

4. Set f = 1 (to store factorial result)

5. Repeat from i = 1 to n:

• Multiply f by i (f = f * i)
• Increment i by 1

6. Print f (final factorial value)

7. Stop

Pseudo code:

START
DECLARE f, n
INPUT n
IF n < 0 THEN
PRINT "Error: Factorial is not defined for negative numbers"
EXIT
ENDIF
SET f = 1
FOR i = 1 TO n
f = f * i
PRINT f
END

C Program:

#include <stdio.h>
int main() {
int n, f = 1, i;
// Ask for user input
printf("Please enter a non-negative number: ");
scanf("%d", &n);
// Check if the input is negative
if (n < 0) {
printf("Error: Factorial is not defined for negative numbers.\n");
} else {
// Calculate factorial
for (i = 1; i <= n; i++) {
f = f * i;
}
// Display the result
printf("The factorial of %d is %d\n", n, f);
}
return 0;
}

Output (Valid Input):

Please enter a non-negative number: 4The factorial of 4 is 24

Output (Invalid Input - Negative Integer):

Please enter a non-negative number: -3Error: Factorial is not defined for negative numbers.

Explanation:

• The program asks the user to enter a number.
• It checks if the input is negative.

• If n is negative, it displays an error message and exits.
• If n is non-negative, it calculates the factorial using a loop.
• The loop starts at 1 and runs until n, multiplying f by i at each step.
• Once the loop ends, the final factorial result is printed.

Example 2: Check if a Number is Even or Odd

Pseudo code:

START
DECLARE number
DISPLAY "Enter a number:"
INPUT number
IF number % 2 == 0 THEN
PRINT "The number is even"
ELSE
PRINT "The number is odd"
END IF
END
C Program:
#include <stdio.h>
int main() {
int number;
// Ask for user input
printf("Enter a number: ");
scanf("%d", &number);
// Use ternary operator to check if the number is even or odd
(number % 2 == 0) ? printf("The number is even\n") : printf("The number is odd\n");
return 0;
}

Output (Even Number):

Enter a number: 42 The number is even

Output (Odd Number):

Enter a number: 45 The number is odd

Explanation:

• The program asks the user to enter a number.
• It uses the ternary operator to check if the number is divisible by 2.

• If number % 2 == 0 (true), it prints "The number is even".
• Otherwise, it prints "The number is odd".
• The ternary operator provides a more compact form of the standard if-else statement, making the code cleaner without sacrificing clarity.

Also Read: Top 3 Open Source Projects for C [For Beginners To Try]

Now that you know how pseudo code simplifies programming by outlining the logic before coding, let’s explore its usage in advanced algorithms.

Pseudo Code Examples for Advanced Algorithms

In advanced algorithms, pseudo-code helps break down intricate logic into easily understandable steps. It allows for quick iteration and testing of ideas without getting bogged down by syntax, making it an essential tool for designing efficient algorithms.

1. Binary Search Algorithm

Binary search is an efficient algorithm for finding a target value within a sorted array. Here's the pseudo code for binary search:

FUNCTION binarySearch(array, target)
SET low = 0
SET high = length(array) - 1
WHILE low <= high DO
SET mid = (low + high) / 2
IF array[mid] == target THEN
RETURN mid
ELSE IF array[mid] < target THEN
SET low = mid + 1
ELSE
SET high = mid - 1
ENDIF
END WHILE
RETURN -1
END FUNCTION

Explanation: This pseudo code performs a binary search. It keeps halving the search space by comparing the target with the middle element. If the target is found, it returns the index; otherwise, it returns -1.

2. Quicksort Algorithm

Quicksort is a divide-and-conquer algorithm for sorting elements. Here's the pseudo code:

FUNCTION quicksort(array, low, high)
IF low < high THEN
SET pivot = partition(array, low, high)
quicksort(array, low, pivot - 1)
quicksort(array, pivot + 1, high)
END IF
END FUNCTION
FUNCTION partition(array, low, high)
SET pivot = array[high]
SET i = low - 1
FOR j = low TO high - 1 DO
IF array[j] <= pivot THEN
i = i + 1
SWAP array[i] AND array[j]
END IF
END FOR
SWAP array[i + 1] AND array[high]
RETURN i + 1
END FUNCTION

Explanation: Quicksort works by selecting a pivot element and partitioning the array around it. The partition function places the pivot in the correct position, and the array is then recursively sorted on both sides of the pivot.

3. Mergesort Algorithm

Mergesort is another divide-and-conquer algorithm, but it divides the array into halves and merges them in sorted order. Here's the pseudo code:

FUNCTION mergesort(array)
IF length(array) <= 1 THEN
RETURN array
END IF
SET mid = length(array) / 2
SET left = mergesort(array[0...mid - 1])
SET right = mergesort(array[mid...end])
RETURN merge(left, right)
END FUNCTION
FUNCTION merge(left, right)
SET result = []
WHILE left AND right ARE NOT EMPTY DO
IF left[0] <= right[0] THEN
APPEND left[0] TO result
REMOVE first element FROM left
ELSE
APPEND right[0] TO result
REMOVE first element FROM right
END IF
END WHILE
APPEND remaining elements FROM left OR right TO result
RETURN result
END FUNCTION

Explanation: Mergesort divides the array into two halves and recursively sorts them. The merge function combines the sorted halves into one sorted array.

4. Recursive Function Example (Factorial)

Recursion is when a function calls itself to solve a problem. Here's the pseudo code for calculating a factorial using recursion:

FUNCTION factorial(n)
IF n == 0 THEN
RETURN 1
ELSE
RETURN n * factorial(n - 1)
END IF
END FUNCTION

Explanation: The function calls itself with a smaller value of n until it reaches the base case (n == 0). This is a common example of recursion.

Also Read: Tower of Hanoi Algorithm Using Recursion: Definition, Use-cases, Advantages

While pseudo code is a powerful tool for planning and structuring code, it has both advantages and limitations. Let's examine them in detail.

Advantages and Disadvantages of Pseudo Code in C

Pseudo code in C improves readability, simplifies complex logic, and helps plan programs without strict syntax. It bridges the gap between flowcharts, algorithms, and coding, making modifications easy.

However, it cannot be executed or debugged, making error detection difficult. Its flexibility can lead to inconsistencies, misinterpretations, and confusion, especially in larger programs.

Here are some advantages and disadvantages of pseudo code in C:

Also Read: 25 Most Common C Interview Questions & Answers [For Freshers]

Now that you’ve understood the strengths and weaknesses of pseudo-code, let’s assess your knowledge with a few MCQs.

How Well Do You Know Pseudo Code in C? 10 MCQs

The questions cover essential concepts such as the definition, purpose, structure, and best practices of pseudo code.

1. What is pseudo code?

a) A programming language with strict syntaxb) A high-level description of a program’s logic using simple English c) A compiled version of an algorithmd) A type of computer-generated code

2. What is the primary purpose of writing pseudo code before coding?

a) To execute the logic fasterb) To make the code more complexc) To outline and clarify logic before implementing it in a programming language d) To replace the need for actual coding

3. Which of the following is a characteristic of pseudo code?

a) It follows a specific syntax like Cb) It is written in natural language and focuses on logic c) It can be directly compiled and executedd) It must include variable data types

4. Which keyword is commonly used in pseudo code to indicate the beginning of the algorithm?

a) BEGINb) INITc) START d) MAIN

5. Which of the following statements is NOT a best practice for writing pseudo code?

a) Using capitalized keywords for clarityb) Using simple and clear languagec) Writing detailed programming syntax in pseudo code d) Using proper indentation for readability

6. Consider the following pseudo code:

IF marks >= 50
PRINT "Pass"
ELSE
PRINT "Fail"
ENDIF

What type of control structure is used in this pseudo code?

a) Loopb) Conditional (If-Else) c) Function Calld) Recursion

7. How would you represent a loop in pseudo code?

FOR i = 1 TO n b) LOOP ic) REPEAT UNTIL i = n d) Both a and c

8. In pseudo code, how do you indicate that a function is being defined?

FUNC functionName()b) FUNCTION functionName() c) DEF functionName()d) BEGIN functionName()

9. What will be the output of the following pseudo code if the user enters 7?

INPUT num
IF num % 2 == 0
PRINT "Even"
ELSE
PRINT "Odd"
ENDIF

a) Evenb) Odd c) Errord) No output

10. What is a limitation of pseudo code?

a) It cannot be used to describe program logicb) It requires strict syntax to be validc) It cannot be executed by a compiler d) It is difficult to understand

How Can upGrad Help You Master C Programming?

upGrad’s courses provide in-depth training in pseudo code and C programming, helping you structure algorithms, optimize logic, and improve problem-solving skills. By mastering pseudo code, you’ll develop a strong foundation for writing efficient C programs and tackling complex coding challenges.

Take the next step in your programming journey with upGrad and transform your logic into real-world C applications.

Here are some relevant courses you can explore:

• Data Structures & Algorithms
• Advanced SQL: Functions and Formulas
• Learn Basic Python Programming
• JavaScript Basics from Scratch
• AI-Powered Full Stack Development Course by IIITB

You can also get personalized career counseling with upGrad to guide your career path, or visit your nearest upGrad center and start hands-on training today!

Similar Reads:

Explore C Tutorials: From Beginner Concepts to Advanced Techniques
Array in C: Introduction, Declaration, Initialisation and More
Exploring Array of Pointers in C: A Beginner's Guide
Explain the array of structures in C language
C Program to check Armstrong Number
C Program to Find ASCII Value of a Character
Discovering C Operators: An Overview with Types and Examples!
Binary Search in C
Addition of Two Numbers in C: A Comprehensive Guide to C Programming
String Anagram Program in C
Understanding Definitions and Includes in C
Difference between Argument and Parameter in C/C++ with Examples
Compiler vs. Interpreter in Programming
Difference Between If Else and Switch: A Complete Overview
Getting Started with 'Do While' Loops in C
Dynamic Array Creation in C Language

FAQs

1: Can pseudo code include functions and loops similar to C programming?

A: Yes, pseudo code can represent loops, conditionals, and function calls, but in a simplified, human-readable format. It focuses on logic rather than strict syntax.

2: How do you write pseudo code for handling user input in C?

A: Pseudo code uses a simple "INPUT" statement to represent user input. This is similar to using functions like scanf() in C but without specific syntax.

3: Is there a standard syntax for pseudo code?

A: No, pseudo code does not have a strict syntax. However, following a clear and consistent format helps make it understandable for others.

4: How do you represent arrays and loops in pseudo code?

A: Arrays are represented as simple variable lists, and loops are written using "FOR" or "WHILE" with clear conditions. The structure remains logical without programming syntax.

5: Can pseudo code be automatically converted into a C program?

A: No, pseudo code is meant for planning and explanation, not execution. It must be manually translated into C code by following the logic step by step.

6: How does pseudo code help in debugging?

A: It breaks down complex logic into smaller steps, making it easier to find mistakes before writing actual code. This reduces errors and saves debugging time.

7: What is the difference between pseudo code and a flowchart?

A: Pseudo code describes logic using text, while a flowchart represents it visually with symbols like arrows and decision blocks. Both serve as planning tools.

8: Can pseudo code be used for complex algorithms like sorting and searching?

A: Yes, pseudo code is commonly used to outline complex algorithms, helping programmers understand and refine logic before writing detailed code.

9: How do you represent nested loops in pseudo code?

A: Nested loops are written by clearly stating the conditions and using proper indentation for readability. The structure follows logical flow rather than programming syntax.

10: Is pseudo code useful for teamwork in software development?

A: Yes, pseudo code helps teams communicate logic clearly before coding. It ensures everyone understands the structure and reduces errors in implementation.

11: Can AI or compilers generate pseudo code from C code?

A: Some tools attempt to convert C code into pseudo code, but they may not be fully accurate. Manually writing pseudo code ensures better clarity and correctness.

Take a Free C Programming Quiz

Answer quick questions and assess your C programming knowledge

Start Quiz