💾 Embedded Memory Vocabulary

Correct: B. Flash memory is non-volatile — it holds data without power. On most microcontrollers the firmware image (text section + read-only data) is stored in on-chip flash and executed in-place (XIP) or copied to SRAM for faster access. Writing to flash requires erase-before-write at page granularity, making it unsuitable for frequent runtime writes.

Memory type	Volatile?	Typical use
Flash	No	Firmware image, const data
SRAM	Yes	Stack, heap, runtime variables
EEPROM	No	Config, calibration, counters

Correct: B. SRAM (Static Random-Access Memory) is the main runtime memory on a microcontroller. Unlike DRAM it requires no refresh, making it suitable for real-time systems. It holds the call stack for every task, the FreeRTOS heap (from which task stacks and kernel objects are allocated), and all read-write global variables. SRAM is typically 10–100× smaller than flash on the same MCU.

SRAM consumer	Notes
Task stacks	Each RTOS task needs its own stack
Heap	Dynamic allocations; fragmentation risk
.data section	Initialized globals copied from flash at startup
.bss section	Zero-initialized globals cleared at startup

Correct: B. A linker script (also called a scatter file on ARM RVDS/Keil) is a text file — usually with a .ld extension for GNU ld — that tells the linker the memory layout of the target hardware and how to map object file sections into that layout. Every embedded project must have one; without it the linker cannot produce a correctly addressed binary.

Linker script concept	Purpose
MEMORY block	Declares available memory regions and their addresses
SECTIONS block	Maps .text, .data, .bss, etc. to memory regions
Symbols (e.g. _edata)	Provide addresses to startup code for copy/clear loops

Correct: B. The .bss section (Block Started by Symbol) holds global and static variables declared without an explicit initializer (C guarantees they are zero). Because they are all zero, there is no need to store initialization data in flash — the startup code simply does memset(bss_start, 0, bss_size) before calling main(), saving flash space.

Section	Initial value	Stored in flash?	In SRAM?
.bss	Zero	No (size only)	Yes
.data	Non-zero	Yes (init values)	Yes (copy)
.rodata	Constant	Yes (in place)	No

Correct: B. The .data section contains global and static variables with non-zero initial values (e.g., int baud_rate = 115200;). The initial values are stored in flash (in a load region sometimes called .data_init), and the startup code copies them into SRAM before main() runs. This copy loop is typically generated by the linker script symbols _sdata / _edata / _sidata.

Startup step	Action
1. Stack pointer	Set SP to top of SRAM
2. Copy .data	Flash → SRAM for initialized globals
3. Clear .bss	Zero uninitialized globals in SRAM
4. Clock init	Configure PLL and system clocks
5. Call main()	Hand off to application code