Static memory allocation patterns in Embedded C - Step-by-Step Execution

Concept Flow - Static memory allocation patterns

Start Program

↓

Declare static/global variables

↓

Memory allocated at compile time

↓

Program runs using fixed memory

↓

No dynamic allocation during runtime

↓

Program ends, memory freed by OS/hardware

Static memory allocation reserves fixed memory at compile time for variables, used throughout program execution without change.

Execution Sample

Embedded C

int main() {
  static int count = 0;
  count = 5;
  return count;
}

This code declares a static variable 'count' with fixed memory allocated before runtime, assigns 5, and returns it.

Execution Table

Step	Action	Variable	Value	Memory Allocation
1	Program start	count	0 (default)	Memory allocated at compile time
2	Enter main()	count	0	Memory already allocated
3	Assign count = 5	count	5	No new allocation, uses static memory
4	Return count	count	5	Memory unchanged
5	Program end	count	5	Memory freed by system

💡 Program ends, static memory is freed by system automatically

Variable Tracker

Variable	Start	After Step 3	Final
count	0 (default)	5	5

Key Moments - 3 Insights

Why does 'count' keep its value between function calls?

Because 'count' is static, its memory is fixed and retains value throughout program execution as shown in execution_table steps 1 to 5.

Is memory allocated for 'count' during runtime?

No, memory for 'count' is allocated at compile time before the program runs, as shown in execution_table step 1.

Can static memory size change during program execution?

No, static memory size is fixed at compile time and does not change during runtime, unlike dynamic allocation.

Visual Quiz - 3 Questions

Look at the execution table, what is the value of 'count' after step 3?

A 5

B 0

C Undefined

D 10

💡 Hint

Check the 'Value' column for 'count' at step 3 in the execution_table.

At which step is the memory for 'count' allocated?

A Step 4

B Step 3

C Step 1

D Step 5

💡 Hint

Look at the 'Memory Allocation' column in execution_table to find when memory is allocated.

If 'count' was not static, what would change in the execution?

A Value of 'count' would persist between program runs

B Memory would be allocated at runtime inside main()

C Memory would be allocated at compile time

D Program would not compile

💡 Hint

Static means compile-time allocation; without static, memory is allocated at runtime.

Concept Snapshot

Static memory allocation reserves fixed memory at compile time.
Variables keep their values throughout program execution.
Memory size and location do not change during runtime.
Used for static and global variables in embedded C.
No overhead of dynamic allocation or deallocation.

Full Transcript

Static memory allocation in embedded C means reserving memory for variables before the program runs. Variables declared as static or global get fixed memory at compile time. This memory stays allocated and retains values throughout the program's life. For example, a static int variable 'count' starts with default zero, then when assigned 5 in main(), it keeps that value until the program ends. No new memory is allocated during runtime for static variables. This makes static allocation predictable and efficient for embedded systems where memory is limited. The program ends and the system frees the memory automatically.