4 x 7 Segment Display Multiplexing

I am using 89S51 and will use P0 and P1 for display
P0 and P1 can not source/sink enough current to give you a bright Display. So you have to use a driver IC.

Take a look to MAX7219 on http://www.maxim-ic.com

Here is my example-Programm

//**********************************************************************
//  C-Programm for driving a MAX7219
//  a 8 digit number is printed in a string (sprintf)
//  and then send to the MAX7219
//**********************************************************************
#include<c8051f200.h>
//#include<math.h>
//#include<string.h>
#include<stdio.h>

sbit Data7219 = P1^0;
sbit Load7219 = P1^1;
sbit Clk7219 = P1^2;

const unsigned char Font_B[16]=
{
        0x7e,0x30,0x6d,0x79,0x33,0x5b,0x5f,0x70,
        0x7f,0x7b,0x77,0x1f,0x4e,0x3d,0x4f,0x47
};

void Send7219 (char,char);
void Send7219byte(char);
void MAX7219init();
void Display(unsigned long int);
//**********************************************************************
void main (void)
{
        MAX7219init();
        Display(47110815);//my_weird_number
        while(1){}
}
//**********************************************************************
void MAX7219init()
{
        Data7219 =0;
        Load7219 =0;
        Clk7219 = 0;
        Send7219(0x09,0x00);//Decode Mode
        Send7219(0x0A,0x05);//Brightness
        Send7219(0x0B,0x07);//Scan limit
        Send7219(0x0C,0x01);
        Send7219(0x0F,0x00);
}
//**********************************************************************
void Send7219 (char Digit,char Data)
{
        Send7219byte(Digit);
        Send7219byte(Data);
        Data7219=0;
        Load7219=1;
        Load7219=0;
}
//**********************************************************************
void Send7219byte (char byte)
{
unsigned char I;
        for(I=0;I<8;I++)
        {
        if (byte & 0x80)
                Data7219=1;
        else
                Data7219=0;

        Clk7219=1;
        byte<<=1;
        Clk7219=0;
        }
}
//**********************************************************************
void Display (unsigned long int My_number)
{
        unsigned char i,string[8];
        sprintf(string,"%8.lx",My_number);
        for (i=0;i<8;i++)
        {
                if (string[i] == 0x20)//0x20 is ASCII " "
                Send7219(i+1,0);          //send MAX7219 " " to MAX7219
                else    if (string[i] <= 0x39)
                                Send7219(i+1,Font_B[string[i] - 0x30]);//0-9
                                else
                                Send7219(i+1,Font_B[string[i] - 0x57]);//A-F
        }
}
//**********************************************************************