The program is modified as follows: (mainly because your loop is written incorrectly, the input character should be -'0' corresponding to the normal number)

# include & ltstdio.h & gt

# include & ltmath.h & gt

int candp(int a，int b，int c)

{ int r = 1；

int s；

int I = 1；

for(I = 1； I < = b; i++)r = r * a；

printf("%d\n "，r)；

s = r % c；

printf("%d\n "，s)；

Return to s; }

void main()

{

Intermediate p, q, e, d, m, n, t, c, r

char s；

Printf ("Please enter p, q:");

scanf("%d%d "，& ampp & amp； q)；

n = p * q；

t =(p- 1)*(q- 1)；

Printf(" n is% 12d\n ",n);

Printf ("Please enter e:");

scanf("%d "，& ampe)；

while(e & lt； 1 | | e & gt； N) // Change this to a while loop.

{

Printf("e is an error, please re-enter: ");

scanf("%d "，& ampe)；

}

d = 1；

while(((e*d)%t)！ = 1)d++；

Printf ("and then calculate that d is %d\n", d);

Printf ("Please enter1\ n" for password);

printf(" plain please input 2 \ n ")；

scanf("%c "，& amps)；

while((s-'0 ')！ = 1。 & amp(s-'0 ')！ =2) // Remove the following getchar () here and add a while loop to pay attention to the characters in brackets.

{scanf("%c "，& amps)； }

Switch (s-'0')

{

case 1:printf(" input the m:")；

scanf("%d "，& ampm)；

c=candp(m，e，n)；

Printf ("Plain is %d\n", c); Break;

Case 2:printf ("input c:");

scanf("%d "，& ampc)；

m=candp(c，d，n)；

Printf ("Password is %8d\n", m); Break;

}

}