c中有多个子函数时，不能正确接收输入的数字

Question

#include<stdio.h>
void prog1_1()
{
int k;
float x=3.6f;
printf("[k=x]=%d [x]=%f [k]=%d\n",k=x,x,k);
printf("[k=x]=%d [x]=%.1f [k]=%d\n",k=x,x,k);
}
void prog1_2()
{
char cData;
int iNum;
float fData;
printf("\ninput a char:");
scanf("%c",&cData);
printf("cData的值是%c\n",cData);
printf("cData占的内存为%d字节\n",sizeof(cData));
printf("cData起始地址是Ox%x\n",&cData);
printf("\ninput an integer:");
scanf("%d",&iNum);
printf("iNum的值是%d\n",iNum);
printf("iNum占的内存为%d字节\n",sizeof(iNum));
printf("iNum起始地址是%#x\n",&iNum);
printf("\ninput a float:");
scanf("%f",&fData);
printf("fData的值是%f\n",fData);
printf("fData占内存为%d字节\n",sizeof(fData));
printf("fData的起始地址是Ox%p\n",&fData);
}
void prog7_1()
{
char c1,c2,c3;
printf("Input three characters:\n");
scanf("%c",&c1);
scanf("%c",&c2);
scanf("%c",&c3);
printf("c1=%c\tASCII=%d\n",c1,c1);
printf("c2=%c\tASCII=%d\n",c2,c2);
printf("c3=%c\tASCII=%d\n",c3,c3);
}
void prog7_2()
{
int m,n;
printf("输入两个数:\n");
scanf("%d,%d",&m,&n);
printf("m=%d,n=%d\n",m,n);
}
void prog5_1()
{
int i=5,j=6,k;
printf("i=%d,j=%d\n",i,j);
i++;++j;
printf("[i++;++j]:i=%d,j=%d\n",i,j);
i--;--j;
printf("[i--;--j]:i=%d,j=%d\n",i,j);
k=(i++)+(++j);
printf("[k=(i++)+(++j)]:i=%d,j=%d,k=%d\n",i,j,k);
k=(i--)+(--k);
printf("[k=(i--)+(--k)]:i=%d,j=%d,k=%d\n",i,j,k);
i=j=k=7;
printf("[=j=k=7;]:i=%d,j=%d,k=%d\n",i,j,k);
k+=++i;
printf("[k+=++i]:i=%d,j=%d,k=%d\n",i,j,k);
k%=++i;
printf("k%=++i]:i=%d,j=%d,k=%d\n",i,j,k);
k*=j--;
printf("[k*=j--]:i=%d,j=%d,k=%d\n",i,j,k);
}
void prog6_1(){
int a=0x64;
int *pa=&a;
char ch='A';
char *pch=&ch;
printf("整形变量a的值为a=%d\n",a);
printf("整形变量a的指针为&a=%p\n",&a);
printf("指针变量pa的值为pa=%p\n",pa);
printf("指针变量pa的指针为&pa=%p\n",&pa);
printf("字符变量ch的值为ch=%d\n",ch);
printf("字符变量ch的指针为&ch=%p\n",&ch);
printf("指针变量pch的值为pch=%p\n",pch);
printf("指针变量pch的指针为&pch=%p\n",&pch);
}
void prog6_2(){
int a=3,b=4,sum=0;
int *pa,*pb,*psum;
char ch;
char *pch=&ch;
pa=&a;pb=&b;psum=&sum;
printf("指针变量的值：pa=%x  pb=%x  psum=%x\n",pa,pb,psum);
printf("目标变量的值：a=%d   b=%d  sum=%d\n",*pa,*pb,*psum);
*psum=*pa+*pb;
*pch='A';
printf("运算结果：sum=%d ch=%c\n",*psum,ch);
printf("整形指针的+运算：pa=%x  pa+1=%x\n",pa,pa+1);
printf("字符型指针的+运算：pch=%x  pch+1=%x\n",pch,pch+1);
}

int main()

{
prog1_1();
prog1_2();
prog5_1();
prog6_1();
prog6_2();
prog7_1();
prog7_2();
 
return 0;
}

当完全执行程序是到了prog7-1时输入三个字符asd程序并没有按我想的收到，而且prog7_2根本就没让我输入数字。

当注释掉其他子函数，只执行prog7-1，prog7_2时就成功了。

想请教一下这是为什么，如何改进。