how does variables behave in reading functions?

[h.m]

hi, when a variable of a function get value after reading a function, what will happen about it's value in reading the function for the second time, i mean the variable take it's value in the end of the last reading of the function or it takes the initial value in each reading?

tnx alot for your helps

 

[horace1]

hi, when a variable of a function get value after reading a function, what will happen about it's value in reading the function for the second time, i mean the variable take it's value in the end of the last reading of the function or it takes the initial value in each reading?

tnx alot for your helps

variables in functions are allocated and initialised on entery to the function
e.g. every time this function is called x has the value 10 - the value at the end of the function (30 is this case is lost)

void test(void)
{
    int x=10;
    ..
    x+=20;
    ..
}

if you wish a variable in a function to retain its value on exit declare it static, e.g.

void test(void)
{
    static int x=10;
    ..
    x+=20;
    ..
}

on first call x will be 10 (and allocated permenant memory until program termination), on subsequenct calls will take whatever value was on previous exit

 

[FvM]

The thread is posted in the FPGA section, so it should be referring to VHDL or Verilog functions. There's no "static" variable in HDL.

 

[h.m]

thank you both of you, yeah i want it in vhdl

 

[TrickyDicky]

when you call a function, all variables inside the function are re-initialised (because they only exist within the scope of the function)