Students grades without 2d arrays C++

#include <iostream>

using namespace std;

// amount of students
#define ROW 5
// amount of subjects
#define COL 4

char getGrade(int x);

int main(){

string student[ROW]={};
/*
each student
has a seperate
array for total
amount of subjects

requirements is 5
students
*/
double s1[COL]={};
double s2[COL]={};
double s3[COL]={};
double s4[COL]={};
double s5[COL]={};
char grades[COL]={};
double percent,t1,t2,t3,t4,t5;
int s=0,c=0,average;

for(int d=0;d<ROW;d++){
cout<<"\nENTER <student> NAME\n";
cin>>student[d];
if(s==COL)s=0; // reset
c=COL;
    while(s<COL){
    cout<<(c--)<<" Enter grade percent\n";
    cin>>percent;
        if(percent<0||percent>100)
            {cout<<"ERROR ENTER PERCENT AGAIN!!\n";
            c+=1; //reset count
            continue;
        }
        switch(d){
            case 0:s1[s]=percent;break;
            case 1:s2[s]=percent;break;
            case 2:s3[s]=percent;break;
            case 3:s4[s]=percent;break;
            case 4:s5[s]=percent;break;
        }//end switch
        s++;
    } //while
 } // for
cout<<endl<<endl<<endl;
//create grades
for(int i=0;i<ROW;i++){
    for(int p=0;p<COL;p++){
        switch(i){
            case 0:(average)=((round(t1+=s1[p]))/COL);break;
            case 1:(average)=((round(t2+=s2[p]))/COL);break;
            case 2:(average)=((round(t3+=s3[p]))/COL);break;
            case 3:(average)=((round(t4+=s4[p]))/COL);break;
            case 4:(average)=((round(t5+=s5[p]))/COL);break;
        }//end switch
    } //.end inner fot
       grades[i]=getGrade(average);
/* Could just call the grades() function in cout
   but the requirements it to store the grade in
   an char array
   */
    cout<<(i+1)<<". "<<student[i]<<" Average is "<<average<<"\n"
    "This student recived an [[ "<<grades[i]<<" ]] to show "
    "the amount of effort\nput in for the year\n\n";

} // end outer for

return 0;
}

char getGrade(int x){

#ifdef __linux__
// for GCC
cout<<"linux\n";
    switch(x){
        case 80 ... 100:return 'A';
        case 70 ... 79:return 'B';
        case 60 ... 69:return 'C';
        case 50 ... 59:return 'D';
        case 40 ... 49:return 'E';
    }
#elif _WIN32
cout<<"windoz\n";

//  METHOID FOR WINDOWS

if(x>=80&&x<=100) return 'A';
else if(x>=70&&x<=79)return 'B';
else if(x>=60&&x<=69)return 'C';
else if(x>=50&&x<=59)return 'D';
else if(x>=40&&x<=49)return 'E';
#endif

return 'F';
}