Published: December 7, 2025 | Reading Time: 6 minutes
This comprehensive guide covers:
How does your browser remember the last page you visited? How do programming languages manage nested function calls? How are expressions evaluated behind the scenes?
All of these rely on one powerful data structure: the stack.
Whether you are building algorithms, preparing for technical interviews, or mastering data structures, understanding how a stack using an array in C works is essential. Array-based stacks offer speed, predictable memory usage, and form the foundation for many real-world systems, from compilers to operating systems.
In this guide, you will learn:
By the end, you'll not only understand stacks, but you will also be able to implement, debug, and use them confidently in your own programs.
A stack is one of the primary linear data structures that stores data in a particular order, following the Last In, First Out (LIFO) principle. Simply put, the last element inserted into the stack is the first one to be removed. Stacks are fundamental to many programming tasks, including expression evaluation, backtracking, and function call management.
Linear Data Structure:
LIFO Principle:
Basic Operations:
Function Call Management:
Expression Evaluation:
Backtracking Algorithms:
Memory Management:
Fixed-Size (Array-Based) Stacks:
Node Struct and Pointer Logic (Linked List-Based):
Struct Definition and Function Declarations:
Stack Overflow refers to pushing an element onto a full stack (in fixed-size implementations). Performing proper checks and handling errors correctly are the only ways to ensure your program won't crash or that memory won't be overwritten.
Stacks provide multiple operations that allow effective data management. When implementing a stack using array in C, understanding each operation is crucial.
The push operation adds a new element to the top of the stack. Before performing this operation, it is essential to check if there is enough space in the stack to avoid overflow.
Example:
void push(int value) {
stack[++top] = value; // Add value to top
printf("Pushed %d\n", value);
}
The pop operation removes the element at the top of the stack. Before performing this operation, it is important to check whether the stack is empty to prevent underflow errors.
Example:
void pop() {
top--; // Remove top element
printf("Popped element\n");
}
The peek operation returns the top element from the stack without removing it. This is useful when application logic needs to access the last saved value while preserving the stack. When implementing a stack using array in C, this operation is the most efficient way to access the top element without changing the data structure.
Example:
void peek() {
printf("Top element: %d\n", stack[top]); // Show top element
}
The display function prints all elements stored in the stack, starting from the top. This helps in understanding the stack's current status.
Example:
void display() {
for (int i = 0; i <= top; i++) { // Print each element
printf("%d ", stack[i]);
}
printf("\n");
}
The isEmpty() function checks if the stack is empty. It returns 1 (true) if the stack is empty, and 0 (false) otherwise. This function helps avoid underflow errors during operations like pop() and peek().
Example:
int isEmpty() {
return top == -1; // Returns true if empty
}
The isFull() method determines whether a stack has reached its maximum capacity. This is useful in preventing stack overflow errors that may result from inserting new elements when the stack is full.
Example:
int isFull() {
return top == MAX - 1; // Returns true if full
}
Using an array to implement a stack in C is a good learning practice. Below are important points that justify this approach:
Arrays are fundamental data structures in most programming languages, making them easy to utilize for stack implementation. This simplicity is a great advantage for beginners learning data structures.
Arrays allocate memory contiguously, making memory consumption more efficient than scattered memory allocation. For example, linked list structures require more memory as they must store reference fields.
Operations like push (insertion) and pop (deletion) can be performed in constant time, O(1), when using arrays, since these merely involve adding or removing elements from the end of the array.
Direct access to elements is achieved through array indices, which is particularly helpful for the peek operation (viewing the top element).
Since each array has a predetermined size, memory allocation is very predictable, which can be a great advantage in resource-constrained systems where memory handling is critical.
Arrays do not require additional memory for pointers, leading to efficient memory utilization compared to linked lists.
Arrays offer an easy method of implementing stacks, making them perfect for those just starting to learn data structures.
Arrays, due to their contiguous memory allocation, improve cache locality, which brings about quicker access times.
Memory allocation is predictable and efficiently managed because the array size is determined beforehand.
When using arrays, there is no need for dynamic allocation or deallocation of memory during stack operations, reducing complexity.
The stack size must be fixed beforehand; exceeding this limit may result in stack overflow.
Arrays cannot change their size dynamically during runtime, making it difficult to handle situations when data loads vary.
To enlarge the stack, a bigger new array must be created and existing elements copied over, which is a time-consuming process.
Only the top element can be directly accessed in a stack; accessing other elements requires additional operations.
If an application requires frequent stack size changes, array-based implementation would be less efficient than a dynamic structure.
| Feature / Aspect | Static Array Stack (Fixed-Size Array) | Dynamic Array Stack (Resizable Array) |
|---|---|---|
| Memory Allocation | Uses contiguous memory allocated at compile-time | Uses dynamic memory allocation at runtime |
| Size Flexibility | Fixed-size array cannot grow beyond predefined maximum capacity | Supports dynamic resizing, growing as needed |
| Risk of Stack Overflow | High risk when stack reaches its fixed limit | Low risk; stack resizes before overflow unless memory is exhausted |
| Performance Overhead | No overhead; operations are fast and predictable | Resizing creates performance overhead due to copying elements |
| Cache Locality | Excellent cache locality due to contiguous memory layout | Good initially, but may degrade after resizes if memory blocks move |
| Direct Memory Access | Very fast direct memory access using indices | Access is still fast, but occasional reallocations may affect performance |
| Memory Efficiency | Wastes memory if array is oversized | Efficient for varying workloads; memory grows only when required |
| Implementation Complexity | Simple to implement; best for beginners | More complex due to reallocation logic |
| Top Variable Handling | Simple top variable updates (+1 / -1) | Same logic, but top must stay consistent through resizes |
| Use Cases | Predictable workloads, embedded systems, limited memory environments | Applications with unpredictable or large input sizes |
| Comparison to Linked List-Based Stack | No pointer overhead; faster access | Still faster access than linked list, but resizing cost doesn't exist in linked lists |
#include <stdio.h>
#include <stdlib.h>
#define MAX 100
int stack[MAX];
int top = -1;
// Sample array to be pushed into stack
int inputArray[] = {10, 20, 30, 40, 50};
int inputSize = sizeof(inputArray) / sizeof(inputArray[0]);
int inputIndex = 0;
// Check if stack is empty
int isEmpty() {
return top == -1;
}
// Check if stack is full
int isFull() {
return top == MAX - 1;
}
// Push operation
void push() {
if (inputIndex >= inputSize) {
printf("No more elements to push from array.\n");
return;
}
if (isFull()) {
printf("Stack Overflow! Cannot push more elements.\n");
return;
}
int value = inputArray[inputIndex++];
stack[++top] = value;
printf("Pushed %d into the stack.\n", value);
}
// Pop operation
void pop() {
if (isEmpty()) {
printf("Stack Underflow! Nothing to pop.\n");
} else {
printf("Popped %d from the stack.\n", stack[top--]);
}
}
// Peek operation
void peek() {
if (isEmpty()) {
printf("Stack is empty.\n");
} else {
printf("Top element is: %d\n", stack[top]);
}
}
// Display stack
void display() {
if (isEmpty()) {
printf("Stack is empty.\n");
} else {
printf("Stack elements: ");
for (int i = 0; i <= top; i++) {
printf("%d ", stack[i]);
}
printf("\n");
}
}
int main() {
int choice;
while (1) {
printf("\n--- Stack Using Array (with predefined input) ---\n");
printf("1. Push Next Element from Array\n");
printf("2. Pop\n");
printf("3. Peek (Top Element)\n");
printf("4. Display Stack\n");
printf("5. Exit\n");
printf("Enter your choice (1-5): ");
scanf("%d", &choice);
switch (choice) {
case 1: push(); break;
case 2: pop(); break;
case 3: peek(); break;
case 4: display(); break;
case 5:
printf("Exiting... Thank you!\n");
exit(0);
default:
printf("Invalid choice! Please enter between 1 to 5.\n");
}
}
return 0;
}
The program also checks:
--- Stack Using Array (with predefined input) ---
1. Push Next Element from Array
2. Pop
3. Peek (Top Element)
4. Display Stack
5. Exit
Enter your choice (1-5): 1
Pushed 10 into the stack.
--- Stack Using Array (with predefined input) ---
1. Push Next Element from Array
2. Pop
3. Peek (Top Element)
4. Display Stack
5. Exit
Enter your choice (1-5): 2
Popped 10 from the stack.
--- Stack Using Array (with predefined input) ---
1. Push Next Element from Array
2. Pop
3. Peek (Top Element)
4. Display Stack
5. Exit
Enter your choice (1-5): 3
Stack is empty.
| Operation | Time Complexity | Space Complexity |
|---|---|---|
| Push | O(1) | O(n) |
| Pop | O(1) | O(n) |
| Peek | O(1) | O(n) |
| Display | O(n) | O(1) |
| isEmpty() | O(1) | O(1) |
| isFull() | O(1) | O(1) |
Stacks are widely used across software systems, programming languages, and operating systems because of their predictable LIFO (Last In, First Out) behavior. Their role goes beyond basic data handling; they are deeply embedded in program execution, memory processing, navigation systems, and undo operations.
Backtracking is a technique used in many algorithms where the program must revert to an earlier state when a branch of the decision tree fails. Algorithms using backtracking include:
Stacks keep records of all previous states. If a certain path doesn't work out, the algorithm removes the last state from the stack and continues from the appropriate point.
Web browsers use stacks to implement Back navigation:
Undo and Redo functions in text editors, graphics software, and IDEs are made possible by stacks:
The LIFO architecture makes doing and undoing operations fast and feasible.
Stacks are essential for:
Compilers implement stacks while converting infix expressions to postfix and when evaluating them.
During syntax analysis, stacks are used to:
Compilers use stacks for symbol tables and semantic checks.
All programming languages use a call stack to keep track of function calls. When a function runs, a stack frame is generated containing:
When the function terminates, the stack frame is popped, and control returns to the calling function.
Operating Systems keep track of:
Stack memory is quick, self-operating, and foreseeable, making it very important for efficient program execution.
Every recursive call adds a new stack frame. Extremely deep recursion will result in stack overflow because memory is limited. This is why some languages have tail recursion optimization.
Systems may perform parallel operations requiring separate stacks:
Such systems might use several stacks to separate different execution contexts.
Note: Stacks are a favorite data structure in real-world systems due to their LIFO nature, which makes state management both predictable and efficient. Stacks are at the core of function calls, expression evaluation, backtracking, undo/redo, and browser navigation. They are also important in compilers, operating systems, and memory management, where structured and reversible execution is essential.
Ensuring your stack implementation is correct and reliable is as important as writing the code itself. Effective testing and debugging strategies help uncover subtle bugs, confirm correct behavior, and improve code quality.
Proper testing and debugging of the stack guarantees that all operations will perform as intended, avoiding errors such as overflow, underflow, and memory corruption. This is very important since stacks lie at the core of expression evaluation, function calls, and backtracking, where a tiny bug might break the entire program flow.
Writing robust and efficient stack code in C is not just about basic operations. By adhering to practical tips and best practices, you can avoid common pitfalls and make your stack implementation dependable, easy to follow, and project-compatible.
When working with stacks implemented using arrays, robust error handling is critical to prevent bugs, crashes, and security issues. Two primary errors can occur: stack overflow and stack underflow.
A stack overflow occurs when an attempt is made to add a new element to a stack that has already reached its maximum limit. This can escalate to a buffer overflow situation where adjacent memory gets overwritten, leading to undefined program behavior.
How to handle:
Stack underflow occurs when attempting to pop or peek from a stack that doesn't contain any elements. This can cause the program to fetch invalid memory or return "garbage" values.
How to handle:
Programmers frequently make off-by-one errors when dealing with stack implementations, such as initializing top incorrectly or choosing incorrect comparisons for full/empty checks, causing subtle bugs.
Best practices:
When an array size is too large, it unnecessarily wastes memory, while a smaller array increases the risk of overflow. Your stack's maximum size should be balanced according to its expected usage.
If something goes wrong in stack functions, the functions should return error codes (like -1 or a user-defined constant) and print clear error messages to let the user know what is wrong, facilitating the debugging process.
Write complete test cases that handle:
Memory for static arrays is allocated during compilation; therefore, there is no need to free it manually. However, always ensure you don't go outside the buffer to avoid memory corruption.
| Error Condition | Cause | Prevention / Handling Strategy |
|---|---|---|
| Stack Overflow | Push attempted when stack has reached capacity | Check isFull() before every push; return error or message |
| Stack Underflow | Pop or peek attempted when stack is empty | Check isEmpty() before pop/peek; handle underflow safely |
| Off-by-One Errors | Incorrect updates to top index (top++, top--) | Initialize top = -1; validate index boundaries strictly |
| Buffer Overflow | Writing beyond array boundary (top >= MAX) | Never allow top to exceed MAX - 1; enforce capacity check |
| Invalid Top Access | Accessing stack[top] when top == -1 | Validate top before reading; return safe error indicator |
| Oversized Arrays | Allocating unnecessarily large arrays | Choose capacity based on expected workload; avoid memory waste |
| Capacity Mismanagement | Using inconsistent MAX size across functions | Centralize MAX definition; keep stack structure consistent |
| Uninitialized Variables | Forgetting to initialize top | Always initialize top = -1 at program start |
The C programming language is a good tool to demonstrate how stack operations work with the help of arrays. Array-based stacks have certain drawbacks, such as limited size and possible memory wastage; however, they are easy to implement and quite efficient for applications that don't require dynamic resizing.
By mastering stack operations, you will be able to work with this data structure in various algorithms and programming tasks, making it an indispensable concept in the field of computer science and software development.
LIFO stands for "Last In, First Out." This means that the last element added to the stack will be the first one removed. All stack operations are based on this principle.
When a stack is implemented with an array, a fixed-size array is used for storing stack elements, and an integer variable (for instance, top) is employed for keeping track of the top position. Stack operations (push, pop, peek, isEmpty, isFull) change the array and accordingly update top.
The most frequently occurring pitfalls are:
Stack initialization involves setting the top variable to -1, which indicates that the stack is empty. In case of using dynamic memory for the array, make sure it is properly allocated before carrying out stack operations.
Utility functions make stack operations safe and efficient:
Stacks track function calls by placing in stack frames return addresses, parameters, and local variables. Compilers utilize stacks while parsing expressions, managing scopes, and supporting recursion.
Stacks facilitate the conversion process (e.g., infix to postfix) or the actual evaluation of postfix expressions by temporarily holding operators and operands. Concerning backtracking algorithms, stacks serve as a tool for storing previous states, enabling the "going back" operation that is necessary most of the time.
Memory for the stack is allocated when the array is defined (either statically or dynamically). No additional memory management is required during push or pop operations, but you must ensure you don't exceed the array's capacity.
A stack frame is a section of the call stack containing information about a single function call, such as local variables, parameters, and the return address. Each time a function is called, a new stack frame is pushed onto the stack; it is popped when the function returns.
Utility functions and error checks prevent common bugs like overflow and underflow, ensure safe memory access, and make your stack implementation more robust and reliable.
Source: NxtWave - CCBP Blog
Original URL: https://www.ccbp.in/blog/articles/stack-using-array-in-c
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