Why Using int as return type in Serialport?

This is a discussion on Why Using int as return type in Serialport? within the C Programming forums, part of the General Programming Boards category; observed that most of the low level serial port routines using int as datatype instead of char .Can anybody explain ...

  1. #1
    Registered User Daffodils's Avatar
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    Why Using int as return type in Serialport?

    observed that most of the low level serial port routines using int as datatype instead of char .Can anybody explain why ?What is the dis advantage if we use char?
    example
    Code:
    
    void init_serial (void)  {               /* Initialize Serial Interface       */
      PINSEL0 = 0x00050000;                  /* Enable RxD1 and TxD1              */
      U1LCR = 0x83;                          /* 8 bits, no Parity, 1 Stop bit     */
      U1DLL = 97;                            /* 9600 Baud Rate @ 15MHz VPB Clock  */
      U1LCR = 0x03;                          /* DLAB = 0                          */
    }
    
    
    /* implementation of putchar (also used by printf function to output data)    */
    
      int sendchar (int ch)  {                 /* Write character to Serial Port    */
    
      if (ch == '\n')  {
        while (!(U1LSR & 0x20));
        U1THR = CR;                          /* output CR */
      }													 																																						
      while (!(U1LSR & 0x20));
      return (U1THR = ch);
    }
    
    
    int getchar (void)  {                     /* Read character from Serial Port   */
    
      while (!(U1LSR & 0x01));
    
      return (U1RBR);
    }

  2. #2
    Registered User
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    It's probably due to the fact that using an int instead of a char allows the function to return an error. The function can return a valid char if it is successful (since a char fits inside an int), but it can then return -1 if the function fails.

    Seeing code like this is pretty common:
    Code:
    #define EOF -1
    
    int getchar(void)
    {
        if(nothing_left)
            return EOF;
        else
            return somechar;
    }
    
    int main(void)
    {
        int ch;
        while((ch = getchar()) != EOF)
        {
            /* Handle the received char */
        }
        ...
    }

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