The logic of your code is to start from the high bit, then multiply by 10 and then accumulate. The idea is okay, but the code is wrong. 1: Do not use commas in the conditional part of the for statement. That is a comma expression, and only the rightmost m>=0 works. 2: The prototype of the pow function is double type. What you want is an integer type. If a strong transformation occurs in the middle, there will be errors. For example, if you enter "100000".

The simplest way is to write a pow function yourself to replace the library function.

The following is changed exactly according to your code:

#include

#include

#include

long pow2(int n,int m)

{

int i;

long sum =1;

for(i=0;i

sum*=n;

return sum;

}

long fun(char *s)

{

int i,n,m;

long sum=0;

n=strlen(s);

m=n-1;

for(i=0;i=0;i++,m --)

sum+=(s[i]-'0')*pow2(10,m);

return sum;

}

int main()

{

printf("Convert the string "2345210" into a numerical value =%ld\n", fun("2345210"));

printf("Convert the string "10000000" into a numerical value =%ld\n", fun("10000000"));

return 0;

}