Program pascal function

contoh : listing program pascal dengan menggunakan fungsi.. 

program tunjangan;
uses wincrt;
var
nm,jab,no :string;
gaj,ti,ta,tgaj:real;
stat,jmlank :integer;
function gajibersih (gaji,tunjangan_anak,tunjangan_istri,totalgaji :real):real;
begin
gajibersih:=gaji+tunjangan_anak+tunjangan_istri;
end;
begin
writeln('=================================================');
    writeln('=TUGAS PERHITUNGAN GAJI DAN TUNJANGAN ANAK ISTRI=');
    writeln('=Nama :Muhammad Asrir           NIM :2010020112 =');
    writeln('=================================================');
    writeln('=  Masukkan data sesuai pada ketentuan berikut  =');
    writeln('=================================================');
    writeln('======Status=====================================');
    writeln('   1. Kawin     ');
    writeln('   2. Tidak Kawin  ');
    writeln('=================================================');
    writeln;
    writeln;
write ('nomor induk karyawan  : ');readln(no);
write ('nama pegawai          : ');readln(nm);
write ('jabatan pegawai       : ');readln(jab);
write ('Gaji pokok            : Rp,');readln(gaj);
write ('status perkawinan       : ');readln(stat);
case stat of
1 :begin
ti :=(15/100)*gaj;
write ('jumlah anak             : ');readln(jmlank);
if (jmlank >=3) then
ta :=(5/100)*gaj
else if (jmlank <3) then
ta :=0;
       end;
2 :begin
ti :=0;
ta :=0;
       end;
   end;
begin
writeln;
    writeln('=================oO SLIP GAJI Oo=================');
    writeln;
    writeln ('Nama          : ',nm);
    writeln ('No Karyawan   : ',no);
    writeln ('Jabatan       : ',jab);
    writeln ('+===============================================+');
    writeln ('|       Rincian Gaji         |      Jumlah      |');
    writeln ('+===============================================+');
    writeln ('| Gaji Pokok               : | Rp ',gaj:8:0,'      |');
    writeln ('| Tunjangan Anak           : | Rp ',ta:8:0,'      |');
    writeln ('| Tunjangan Istri          : | Rp ',ti:8:0,'      |');
    writeln ('|                            |                  |');
    writeln ('+===============================================+');
    writeln ('| Total Gaji Bersih        : | Rp ',gajibersih (gaj,ti,ta,tgaj):8:0,'      |');
    writeln ('+===============================================+');
    readln;
end;
end.