Declaration

Tags: #◇CCPROG2 #◇C Programming #◇Programming #◇Computer Science #◇Data Structures #◇Data Types #◇Structured Programming #◇Memory Management

◇Overview

Array declaration in C specifies the data type, name, and size of the array, allocating a contiguous block of memory.

◇Key Concepts

Syntax: dataType arrayName[arraySize]; Size must be a compile-time constant (in standard C89) or variable-length (C99+) Memory is allocated contiguously Elements are uninitialized by default (contain garbage values)

◇Details / Theory

Syntax

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dataType arrayName[arraySize];

dataType — the type of each element (int, float, char, etc.) arrayName — identifier for the array (follows C naming rules) arraySize — positive integer specifying number of elements

Examples

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int numbers[10];     // Array of 10 integers
float prices[5];     // Array of 5 floats
char name[30];       // Array of 30 characters (for strings)

Memory Allocation

Declaration allocates arraySize × sizeof(dataType) bytes contiguously:

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int arr[10];  // Allocates 10 × 4 = 40 bytes (assuming 4-byte int)

Variable-Length Arrays (VLA) — C99+

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int n;
scanf("%d", &n);
int arr[n];  // Size determined at runtime (C99 feature)

[!tip] Key Insight
VLAs are allocated on the stack and cannot be initialized at declaration.

Multi-Dimensional Declaration

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int matrix[3][4];    // 2D array: 3 rows, 4 columns
int cube[2][3][4];   // 3D array

◇Common Pitfalls

Using a variable as array size in C89 (only allowed in C99+). Forgetting that uninitialized arrays contain garbage values, not zeros. Declaring arrays with size 0 — this is not valid in standard C.

◇Summary

TL;DR — Array declaration in C uses dataType name[size]; to allocate contiguous memory. Size must be a positive constant (C89) or variable (C99+). Uninitialized elements contain garbage values.

◇Links

Related: ◇Initialization — ◇Size — ◇Element Type — ◇Memory Allocation — ◇One-Dimensional Arrays (1D Arrays) Source / Reference:

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Related Notes: ◇Initialization, ◇Memory Allocation

DECLARATION