The storage location of each variable in MCU is ram or flash

I had nothing to do, so I studied the storage location
of variables in MCU. ps: There are three places where data can be stored in MCU: register, rom, and ram.

Standard C keywords involved: register: define and apply for a register-level variable
                          auto: define automatic variables, which are compiler defaults by default
                          const: define constants

involving IAR predefines: __no_init: indicates that the variable does not need to be initialized
                         section .text segment: stores code
                         section .rodata segment: stores read-only data
                         section .noinit segment: stores data that does not need to be initialized
                         section .bss segment: stores default initialized data
                         section .data segment: stores initialized data
                         CSTACK segment: stack
                         HEAP segment: heap

//Attribute: macro variable
//Location: It is assembled into the section .text segment during precompilation (usually placed in rom)
//Operation: It no longer exists during operation
#define ro_def 0x11111111UL

//Attribute: constant, read-only variable
//Location: directly exists in the section .rodata segment (usually placed in rom)
//Operation: All accesses in the program are in section .rodata segment (slower speed)
const uint32_t ro_var = 0x222222222;

//Attribute: Uninitialized global variable
//Location: It exists in section .noinit: DATA segment (usually placed in ram)
//Operation: When accessed in the program, it is accessed in section .noinit: DATA segment (faster speed)
__no_init uint32_t ni_global_var;                 

//Attribute: Default 0 initialized global variable
//Location: It exists in section .bss segment (usually placed in ram)
//Operation: Clear the bss segment at startup; When accessed in the program, it is accessed in section .bss segment (faster speed)
uint32_t zi_global_var;

//Attribute: Initialized global variable
//Location: The initialization value exists in section .data_init segment (usually placed in rom), and the variable itself exists in section .data segment (usually placed in ram)
//Operation: At startup, copy the initial value from the .data_init segment to the .data segment; when accessed in the program, it is accessed in the section .data segment (faster)
uint32_t i_global_var = 0x33333333; 

void test_variable(void) 
{
    //Attribute: Initialized register variable
    //Location: Its initialization value exists in the section .text segment (usually placed in ROM), and the variable itself exists in the CPU's register
    //Operation: If the application is successful, when accessed in the program, it is accessed in the CPU's register (fastest speed); if the application fails, it is an ordinary local variable
    register uint32_t i_register_var = 0x44444444;
    
    //Attribute: Initialized local variable
    //Location: Its initialization value exists in the section .rodata segment (usually placed in ROM), and the variable itself exists in CSTACK (usually placed in RAM)
    //Operation: When defining, copy the initial value from the .rodata segment to the CSTACK; when accessing in the program, it is accessed in the CSTACK segment (faster). It is said that pushing local variables into the stack is just a simple move of the SP pointer to free up space for local variables. Addressing uses the offset of SP as the relative address
    uint32_t i_local_iArray[4] = {0x55555555, 0x66666666, 0x77777777, 0x88888888};

    //Attribute: dynamic memory allocation
    //Location: The value is assigned to the section .text segment, and the requested memory area is in the HEAP (usually in RAM)
    //Operation: When accessing in the program, it is accessed in the HEAP segment (faster)
    uint32_t *zi_local_p;
    p = (uint32_t *)malloc(4);
    ...
}