Unhandled exception at 0x00c71443 0xC0000005: Access violation writing location 0x00000028

I was writing C code to simulate transmitting a character from uart. I am getting the title error.

Code:

#include<stdio.h>
void transmit(char uart, char data[]){
   writeReg(uart,data);
      ......
       ......
}

void writeReg(char addr, char data[]){
  char* dataPtr = data;
  char* regPtr = (char*)addr;
  *regPtr = *dataPtr;  ........ This is where the error was thrown <bad ptr>
}

void main(){
   transmit(0x28,"1245");
}

Your code attempts to write to memory at the location 0x00000028. This address is in a protected region of the address space and you are not allowed to write (or read) there. Hence the access violation.

Your problems begin here:

char* regPtr = (char*)addr;

addr is a char, and in your program it has the value 0x28. You then treat that as an address, and the inevitable consequence is the access violation.

The reason the compiler rejected

char* regPtr = addr;

is that addr is not a char*. Simply casting does not change that fact. When you are faced with a compilation error that you do not understand, do not attempt to cast your way past it. Step 1 is always to understand the error.

Your code makes no real sense. I don't know what it tries to do, so I cannot tell you what the code should be.