下列程序的功能是：求出ss字符串中指定字符c的个数，并返回此值。请编写函数int num（*char ss,char

下列程序的功能是：求出ss字符串中指定字符c的个数，并返回此值。请编写函数int num(*char ss,char c)以实现程序要求，最后调用函数readwriteDat()，把结果输出到文件out.dat中（注：大小写字母有区别）。例如：若输入字符串“ss="123412132" , c=’1’”，则输出“3”。部分源程序已给出。请勿改动主函数main()和输出数据函数writeDat()的内容。#include ＜conio.h＞#include ＜stdio.h＞#define M 81void readwriteDAT(); int num(char *ss,char c){ } main(){ char a[M],ch; clrscr(); printf("\nPlease enter a string:" );gets(a); printf("\nPlease enter a char;" );ch=getchar(); printf("\nThe number of the char is:%d\n" ,num(a,ch)); readwriteDAT();}viod readwriteDAT(){ int i; FILE *rf,*wf; char a[M],b[M],ch; rf=fopen("in.dat" ,"r" ); wf=fopen(" out.dat" ,"w" ); for(i=0;i＜10;i++){ fscanf(rf," %s",a); fscanf(rf," %s" ,b); ch=*b; fprintf(wf," %c=%d\n:" ,ch,num(a,ch));} fclose(rf); fclose(wf);}