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C language learned by suffering
C language learned by suffering

I want to use dynamic arrays & malloc

I want to declare a dynamic array using malloc, but I don't know how.
First of all, malloc is not necessary for a beginner's program.
Modern PCs are not scared by arrays as small as char s[1000000];.
The opposite is also true for embedded systems, where mallocs should be refrained from to save memory.
With this in mind, please read the following usage.

Allocate memory in the following way, even for non-int types. Even structures.
int *data;
data = malloc(sizeof(int) * number of elements needed);

The allocated memory can be used in the same way as an ordinary array.
data[i] = 10;

If you want to increase the number of elements, do the following
data = realloc(data,sizeof(int) * number of elements needed);

When the array is no longer used, it can be freed in this way.

Note that for very small programs, there is no problem even if the free function is not used.
If you forget to deallocate the memory in a large program, it will cause the program to become slower and slower as it runs.
Therefore, be sure to call the free function to get into the habit of deallocation.

About this Site

The C language (bitter C), which is learned by suffering, is
This is the definitive C language introductory site.
It systematically explains the basic functions of the C language and
It is as complete as or better than any book on the market.

Part 0: Program Overview
  1. What is the program?
Chapter 2: How to write a program
  1. Writing Rules
  2. Writing conventions
  3. Exercise 2
Chapter 3: Display on Screen
  1. String display
  2. newline character
  3. Exercise 3
Chapter 4: Numeric Display and Calculation
  1. Numeric Display
  2. Basic Calculations
  3. Type of value
  4. Exercise 4
Chapter 5: Numerical Memory and Calculation
  1. Memorize values
  2. Variable Type
  3. Type conversion
  4. Numeric justification
  5. Exercise 5
Chapter 6: Input from the keyboard
  1. Functions for input
  2. Fear of Input
  3. Exercise 6
Chapter 9: Repetition with a fixed number of times
  1. Sentences that repeat themselves
  2. Loop Operation Mechanism
  3. Exercise 9
Chapter 10: Unknown number of repetitions
  1. Loop of unknown frequency
  2. input check
  3. Exercise 10
Chapter 13: Handling Multiple Variables at Once
  1. Multiple variables are handled together.
  2. How to use arrays
  3. Exercise 13
Chapter 19: Dynamic Arrays
  1. Create arrays at will
  2. Exercise 19
Chapter 20: Multiple Source Files
  1. Minimal division
  2. The Stone of Partition
  3. Exercise 20


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