Acces Violation and "memory could not be read"

[brent.banaag]

Please help me. The following program builds and compiles just fine however when I try to execute it it stops before getting any output, displaying "The instruction at "0x77c48a0b" referenced memory at "0x00000014". The memory could not be "read"". I also get the following when the debugger reaches the point where I input for the switch-case variable: "An Access violation (Segmentation fault) is raised in the program."

**I'm practicing files hehe :/

#include<stdio.h>
#include<conio.h>
#include<string.h>
#include<cstdlib>

void createFile(char fileName[])
{
    FILE *fp;
    fopen(fileName,"w");
    fclose(fp);
}
void writeFile(char fileName[],char content[])
{
     FILE *fp;
     fopen(fileName,"w");
     if(fp==NULL)
     printf("error 404: file not found");
     else
     {
         fwrite(content,strlen(content),sizeof(content),fp);
         printf("Write your desired content");
         scanf("%s",content);
     }
     fclose(fp);
}

void displayFile(char fileName[],char content[])
{
     FILE *fp;
     char temp[50];
     fopen(fileName,"r");
     if(fp==NULL)
     printf("error 404: file not found");
     else
     {
                 fseek(fp,SEEK_SET,0);
                 fread(temp,strlen(content),sizeof(content),fp);
                 printf("%s\n",temp);
     }
     fclose(fp);
}    
int main()
{
    char a[50], b[50];
    char choice;
    printf("A to create the file, B to write on the file, or C to display the file's content: ");
    scanf("%c",&choice);
    switch(choice)
    {
                  case 'A':{
                       printf("Create the filename: ");
                       scanf("%s",a);
                       fflush(stdin);
                       createFile(a);
                       } break;
                  case 'B': writeFile(a,b); break;
                  case 'C': displayFile(a,b); break;
                  default: break;
    }
    getch();
    system("pause");
    return 0;
}

[Moschops]

You have a pointer, fp, that you create and use but you never, ever set it to anything. It will be pointing to some random location in memory. This is very bad.