24 hr to 12 hr and vice versa getting error pls help

[naysa]

#include<iostream.h>
#include<conio.h>
#include<string.h>
void choice(int c);
void display(int hrs,int mins,char m[]) ;

void to_24(int& hrs,char& m) ;
void to_12(int& hrs) ;
void input(int c,char m[]) ;
int hrs,mins,c;
char m[10];
int main()
{

void choice(int c);
// if c==1
void input(int c,char m[]);
if (!strcmp(" ",m))// m == " ")
// (!strcmp("AM",m))
to_12(hrs);

else
to_24(hrs,m[10]);
void display (int hrs,int mins,char m);
return 0;
}

void choice( int c)
{
cout<<"Enter your choice:"<<endl;
cout<<"Press 1 to convert into 12 hr notation"<<endl;
cout<<"Press 2 to convert into 24 hr notation"<<endl;

cin>>c;
}

void display(int hrs,int mins,char m[])
{
if ( m==" " )
cout<< "The time in 24hr notation is:" <<hrs<<":"<<mins<<" <<"<<m<<endl;
else
cout<< "The time in 12 hr notation is:" <<hrs<<":"<<mins<<" "<<m<<endl;

}


void input(int c,char m[])
{
if ( c==1 )
{ cout<< "Enter the number hours ";
cin >> hrs;
cout<< "Enter the number minutes ";
cin >> mins;
m=" "; }

else if ( c==2)
{ cout<< "Enter the number hours ";
cin >> hrs ;
cout<< "Enter the number minutes ";
cin >> mins;
cout<< "Enter AM/ PM ";
cin >> m; }

}

void to_24(int& hrs,char m[10])
{
if (!strcmp("AM",m))
{hrs=hrs;
m=m;
//mins=mins;
}
else if (m == "PM")
{ hrs+12;
}
// return(0);
}
void to_12(int& hrs)
{
char m[10];

if (hrs>12)
{hrs-=12;
memcpy(m,"PM",10) ;
//mins=mins;
}
else if (hrs<12)
{ hrs=hrs;
memcpy(m,"AM",10);
}

}

when i'm compiling in turbo c++ compiler there are no error but when i run

"undefined symbol to_24(int near&,char near&) in module

can some one pls help asap
thank u

[Dy7SLyTq]

a) i would use g++. someone correct me if im wrong but i believe its outdated