void rank2(int n,int m)
{
    int i,j,g;
    student saver;
    printf("%16s%16s%16s","number","name","sum");
    for(g=0;g<=m-1;g++)
        printf("%15s%1d","subject",g+1);
    printf("\n");
    for(i=0;i<=n-1;i++)
    {
        for(j=i+1;j<=n-1;j++)
        {
            if(a[i].number>=a[j].number)
                saver=a[i];
                a[i]=a[j];
                a[j]=saver;
        }
        printf("%16d%16s%16f",a[i].number,a[i].name,a[i].sgrade);
        for(g=0;g<=m-1;g++)
            printf("%16.2f",a[i].grade[g]);
        printf("\n");
    }

请问为什么要初始化为零？