This document explains how a C++ program is stored in RAM, detailing its organization into four segments: text, data, heap, and stack. The text segment contains executable instructions and is read-only, while the data segment holds initialized and uninitialized data. The heap segment is for dynamically allocated memory, and the stack segment stores local variables, managing function calls and local data through stack frames.

1. How C++ program stored in
RAM

2. C/C++ PROGRAM STORED IN RAM MEMORY
The memory layout of program is organized by 4 segments
● Text segment
● Data segment
● Heap segment
● Stack segment

3. C PROGRAM STORED IN RAM MEMORY

4. Text segment
● Text segment contains executable instructions of program, it is also
called code segment.
● The text segment is sharable so that only a single copy needs to be in
memory for different executing programs, such as text editors, shells,
and so on.
● Text segment is read-only, to prevent a program from accidentally
modifying its instructions.

5. Data segment
Two subsections of Data segment
Initialized data
● It contains both static and global data that initialized with non-zero
values.
● This segment can be further classified into the read-only area and read-
write area.

6. Uninitialized data (BSS segment)
● An uninitialized data segment also called the BSS( ‘Block
Started by Symbol’ ) segment.
● Which contains all global and static variables that
initialized to zero or do not have explicit initialization in
source code.

7. Heap segment
● The heap segment is an area where dynamically allocated memory by
using (new).
● When we allocate memory through dynamic allocation techniques(in
other words, run-time memory allocation), program acquire space from
OS and process address space grows
(cont)

8. Heap segment
● We can free dynamically allocated memory space (by using free() or
delete).
● Freed memory goes back to the heap but doesn’t have to be returned
to OS (it doesn’t have to be returned at all), so unordered
malloc/free eventually, cause heap fragmentation.
● When we use dynamic allocation to acquire memory space we must
keep track of allocated memory by using its address.

9. Stack segment
● The stack segment is an area where local variables stored.
● When we call any function, the stack frame created and when a
function returns, the stack frame destroyed/rewind including all local
variables of that particular function.
● A stack frame contains some data like return address, arguments passed
to it, local variables, and any other information needed by the invoked
function.

10. Stack Segment
● A stack pointer(SP) which is a special function register of CPU keeps
track of stack by each push & pop operation onto it, by adjusted stack
pointer to next or previous address.
● The direction of the stack & heap growth completely depends on the
compiler, OS and hardware.