I need help with switch case

I have the problem that after the first run of the addieren() function the default case is triggered and the result of the calculation disappears.

Sorry for my bad english.

Code:

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#include <stdio.h>
#include <stdlib.h>


void wurzel();
void addieren();
void subtrahieren();
void dividieren();
void multiplizieren();
void menue();
void rechenOperator(char rOperator);


int main()
{
    menue();
    char eingabeOperator=NULL;
    printf("\nSchreibe den gewuenschten Rechen-Operator: ");
    eingabeOperator=getchar();


    rechenOperator(eingabeOperator);
}


void menue(){
    printf("\n----- Taschenrechner-Menue -----\n");
    printf("Schreibe 'S' oder 's' um den Rechner zu verlassen \n");


    printf("Schreibe + Symbol fuer Addition \n");
    printf("Schreibe - Symbol fuer Subtraktion \n");
    printf("Schreibe * Symbol fuer Multiplikation \n");
    printf("Schreibe / Symbol fuer Division \n");
    printf("Schreibe 'W' oder 'w' fuer Wurzel \n");
}


void rechenOperator(char rOperator) {


        switch(rOperator) {
            case'+':addieren();
                    break;


            case'-':subtrahieren();
                    break;


            case'*':multiplizieren();
                    break;


            case'/':dividieren();
                    break;


            case's':exit(0); break;


            case'S':exit(0); break;


            case'w':wurzel();
                    break;


            case'W':wurzel();
                    break;


            default:system("cls");
                    printf("Du hast keine korrekte Auswahl eingegeben.\n");
                    main();
                    break;
        }


}


void addieren(){
    float Summand1, Summand2, ergebnis;
    printf("\nErster Summand: ");
    scanf("%f", &Summand1);
    printf("\nZweiter Summand: ");
    scanf("%f", &Summand2);


    ergebnis = Summand1 + Summand2;


    system("cls");
    printf("\n%f + %f = %f\n", Summand1, Summand2, ergebnis);
    main();
}

---

First things first: don't call main(). It's not necessary. If you want to return to the function that called your function, use a return statement.

Second, what do you see if you print out the character that the user types in (as a debugging technique)? Hint: you should remove (or comment out) the system("cls") statements so you can see the previous output.

I see it's working in linux environment.

I made one change of commenting all except addition, to run with out compilation issue.

Also you make use of return even in main().

Though main can be called from any where in the program ,best practice is not to use that as user defined function.

output is as below

Code:

---

./a.out

----- Taschenrechner-Menue -----
Schreibe 'S' oder 's' um den Rechner zu verlassen
Schreibe + Symbol fuer Addition
Schreibe - Symbol fuer Subtraktion
Schreibe * Symbol fuer Multiplikation
Schreibe / Symbol fuer Division
Schreibe 'W' oder 'w' fuer Wurzel

Schreibe den gewuenschten Rechen-Operator: +

Erster Summand: 10.01

Zweiter Summand: 20.02
sh: cls: command not found

10.010000 + 20.020000 = 30.030001

----- Taschenrechner-Menue -----
Schreibe 'S' oder 's' um den Rechner zu verlassen
Schreibe + Symbol fuer Addition
Schreibe - Symbol fuer Subtraktion
Schreibe * Symbol fuer Multiplikation
Schreibe / Symbol fuer Division
Schreibe 'W' oder 'w' fuer Wurzel

sh: cls: command not found
Schreibe den gewuenschten Rechen-Operator: Du hast keine korrekte Auswahl eingegeben.

----- Taschenrechner-Menue -----
Schreibe 'S' oder 's' um den Rechner zu verlassen
Schreibe + Symbol fuer Addition
Schreibe - Symbol fuer Subtraktion
Schreibe * Symbol fuer Multiplikation
Schreibe / Symbol fuer Division
Schreibe 'W' oder 'w' fuer Wurzel

Schreibe den gewuenschten Rechen-Operator: +

Erster Summand: 30.01

Zweiter Summand: 40.02
sh: cls: command not found

30.010000 + 40.020000 = 70.029999

----- Taschenrechner-Menue -----
Schreibe 'S' oder 's' um den Rechner zu verlassen
Schreibe + Symbol fuer Addition
Schreibe - Symbol fuer Subtraktion
Schreibe * Symbol fuer Multiplikation

---

One tip not related to your problem: Don't use 'system("cls");'. It is DOS/Windows specific and dangerous (what if someone put a cls.exe in the directory with a virus?)...

Here's a clearscreen.c for you: Works on Unix terminals who accept ANSI codes and on Windows as well (using GCC):

Code:

---

/* console.h */
#ifndef CONSOLE_H_INCLUDED__
#define CONSOLE_H_INCLUDED__

void clearscreen( void );
void gotoxy( int, int );

#endif

---

Code:

---

/* console.c */
#if defined(__linux) || defined(__APPLE__)
// Linux or MacOS

#include <stdio.h>

/* Uses ANSI codes */
void clearscreen(void) { fputs("\x1b[2J", stdout); }

// coordinates start at (0,0).
void gotoxy(int x, int y) { printf("\x1b[%d;%dH", ++x, ++y); }

#else

#include <windows.h>
/* Uses Windows API */

void clearscreen(void)
{
  HANDLE hConsole;
  COORD coord = { 0 };
  CONSOLE_SCREEN_BUFFER_INFO csbi;
  DWORD dwConsoleSize, dwWriten;
 
  hConsole = GetStdHandle(STD_OUTPUT_HANDLE);
  GetConsoleScreenBufferInfo(hConsole, &csbi);
  dwConsoleSize = csbi.dwSize.X * csbi.dwSize.Y;
 
  FillConsoleOutputCharacter(hConsole, (TCHAR)' ',
                            dwConsoleSize, coord, &dwWriten);
  FillConsoleOutputAttribute(hConsole, csbi.wAttributes,
                            dwConsoleSize, coord, &dwWriten);

  SetConsoleCursorPosition(hConsole, coord);
}

void gotoxy(int x, int y)
{
  HANDLE hConsole;
  COORD coord = { .X = x, .Y = y };
 
  hConsole = GetStdHandle(STD_OUTPUT_HANDLE);
  SetConsoleCursorPosition(hConsole, coord);
}

#endif

---

Now you can use 'clearscreen();'.

Code:

---

include <stdio.h>
#include <stdlib.h>
 
void addieren();
void menue();
void get();
void rechenOperator(char rOperator);
 
int main() {
    menue(); get();
}
 
void menue(){
    printf("\n----- Taschenrechner-Menue -----\n");
    printf("Schreibe 'S' oder 's' um den Rechner zu verlassen \n");
    printf("Schreibe + Symbol fuer Addition \n");
    printf("Schreibe - Symbol fuer Subtraktion \n");
    printf("Schreibe * Symbol fuer Multiplikation \n");
    printf("Schreibe / Symbol fuer Division \n");
    printf("Schreibe 'W' oder 'w' fuer Wurzel \n");
}

void get() {
    printf("\nSchreibe den gewuenschten Rechen-Operator: ");
    char eingabeOperator = getchar();
    rechenOperator(eingabeOperator);
}
 
void rechenOperator(char rOperator) {
    switch(rOperator) {
      case'+':
        addieren();           
      break;

      case's': case 'S':
        exit(0);
      break;
 
      default:
        printf("\nDu hast keine korrekte Auswahl eingegeben.\n");
        get();
      break;
  }
}
 
void addieren(){
    float Summand1, Summand2, ergebnis;
    printf("\nErster Summand: ");
    scanf("%f", &Summand1);
    printf("\nZweiter Summand: ");
    scanf("%f", &Summand2);
    ergebnis = Summand1 + Summand2;
    system("cls");
    printf("\n%f + %f = %f\n", Summand1, Summand2, ergebnis);
    menue();
    get();
}

---

Having a function called 'get' which returns nothing is just weird.

And just pushing the infinite recursion out of main doesn't really make much progress.

Code:

---

#include <stdlib.h>
 
void addieren();
void menue();
char get();
void rechenOperator(char rOperator);
 
int main() {
    while ( 1 ) {
        menue();
        rechenOperator(get());
    }
    return 0;
}
 
void menue(){
    printf("\n----- Taschenrechner-Menue -----\n");
    printf("Schreibe 'S' oder 's' um den Rechner zu verlassen \n");
    printf("Schreibe + Symbol fuer Addition \n");
    printf("Schreibe - Symbol fuer Subtraktion \n");
    printf("Schreibe * Symbol fuer Multiplikation \n");
    printf("Schreibe / Symbol fuer Division \n");
    printf("Schreibe 'W' oder 'w' fuer Wurzel \n");
}
 
char get() {
    printf("\nSchreibe den gewuenschten Rechen-Operator: ");
    char eingabeOperator = getchar();
    return eingabeOperator;
}
 
void rechenOperator(char rOperator) {
    switch(rOperator) {
      case'+':
        addieren();           
      break;
 
      case's': case 'S':
        exit(0);
      break;
 
      default:
        printf("\nDu hast keine korrekte Auswahl eingegeben.\n");
      break;
  }
}
 
void addieren(){
    float Summand1, Summand2, ergebnis;
    printf("\nErster Summand: ");
    scanf("%f", &Summand1);
    printf("\nZweiter Summand: ");
    scanf("%f", &Summand2);
    ergebnis = Summand1 + Summand2;
    printf("\n%f + %f = %f\n", Summand1, Summand2, ergebnis);
}

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