major_scale.c

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

int main (int argc, char const *argv[])
{
  int note, i;
  char key[3];
  char* scale[12] = {"C","Db","D","Eb","E","F","Gb","G","Ab","A","Bb","B"};
  
  printf("Please enter the key (CAPITALS only, use b for flats, e.g. Eb): ");
  scanf("%s", key);

  //use table to translate name to pitch class
  for(i = 0; i < 12; ++i)
  {
    if(strcmp(scale[i], key) == 0) // that means we've found the note
    {
      note = i;
      printf("== %s major scale ==\n", key);
      break;
    }
    else note = -1; //note not found!
  }
  
  if(note >= 0)
  {
    for(i = 0; i < 7; ++i)
    {
      //use table to translate pitch class to note name
      printf("%s ",scale[note%12]);
      if(i != 2) note += 2;
      else note++;
    }
    printf("\n");
    return 0;
  }
  else{
    printf("%s: invalid key\n", key);
    return 1;
  }
  
}