kernel.c: In function ‘KeyboardIsr’:
kernel.c:102: error: ‘byte’ undeclared (first use in this function)
kernel.c:102: error: (Each undeclared identifier is reported only once
kernel.c:102: error: for each function it appears in.)
kernel.c:102: error: expected ‘;’ before ‘new_scan_code’

// Taking input...
unsigned char inportb (unsigned short _port)
{
    unsigned char rv;
    __asm__ __volatile__ ("inb %1, %0" : "=a" (rv) : "dN" (_port));
    return rv;
};

// ...and gathering output.
void outportb (unsigned short _port, unsigned char _data)
{
    __asm__ __volatile__ ("outb %1, %0" : : "dN" (_port), "a" (_data));
};


// It's self explanitory: The Keyboard ISR (and accompanying variables).
void KeyboardIsr()
{
   byte new_scan_code = inportb(0x60);

   /* Do something with the scancode.
    * Remember you only get one byte of the scancode each time the ISR is invoked.
    * (Though most of the times the scancode is only one byte.)
    */

   /* Acknowledge the IRQ, pretty much tells the PIC that we can accept >=priority IRQs now. */
   outportb(0x20,0x20);
}

typedef unsigned char byte;

kernel.c: At top level:
kernel.c:88: error: expected declaration specifiers or ‘...’ before ‘size_t’
kernel.c:89: warning: conflicting types for built-in function ‘memcpy’
kernel.c: In function ‘memcpy’:
kernel.c:92: error: ‘count’ undeclared (first use in this function)
kernel.c:92: error: (Each undeclared identifier is reported only once
kernel.c:92: error: for each function it appears in.)
kernel.c: At top level:
kernel.c:96: error: expected declaration specifiers or ‘...’ before ‘size_t’
kernel.c:97: warning: conflicting types for built-in function ‘memset’
kernel.c: In function ‘memset’:
kernel.c:99: error: ‘count’ undeclared (first use in this function)
kernel.c: At top level:
kernel.c:103: error: expected declaration specifiers or ‘...’ before ‘size_t’
kernel.c: In function ‘memsetw’:
kernel.c:106: error: ‘count’ undeclared (first use in this function)
kernel.c: At top level:
kernel.c:110: error: expected ‘=’, ‘,’, ‘;’, ‘asm’ or ‘__attribute__’ before ‘strlen’

void *memcpy(void *dest, const void *src, size_t count)
{
    const char *sp = (const char *)src;
    char *dp = (char *)dest;
    for(; count != 0; count--) *dp++ = *sp++;
    return dest;
}

void *memset(void *dest, char val, size_t count)
{
    char *temp = (char *)dest;
    for( ; count != 0; count--) *temp++ = val;
    return dest;
}

unsigned short *memsetw(unsigned short *dest, unsigned short val, size_t count)
{
    unsigned short *temp = (unsigned short *)dest;
    for( ; count != 0; count--) *temp++ = val;
    return dest;
}

size_t strlen(const char *str)
{
    size_t retval;
    for(retval = 0; *str != '\0'; str++) retval++;
    return retval;
}

-nosdtinc -nostdlib -fno-builtin