Why the part of findbyname it retuns me "does not exist" and also show me informations

Question

#include<stdio.h>
#include<string.h>
#include<conio.h>
#include<stdbool.h>
int n,m;
struct student{
long int Id;
char name[10];
float score[4];
float math,physics,programming;
float sum;
float avr;
}st[];
void storeinfo(){
printf("Please enter student number : ");
scanf("%d",&n);
for(int i=0;i<n;i++){
printf("\nThe student %d id ",i+1);
scanf("%ld",&st[i].Id);
getchar();
printf("The student name ");
gets(st[i].name);
printf("physics: ");
scanf("%f", &st[i].physics);
printf("math: ");
scanf("%f", &st[i].math);
printf("programming: ");
scanf("%f", &st[i].programming);
printf("\n\n");
}
}
void avr(){
float sum;
float avr;
for(int i=0;i<n;i++){
sum=st[i].programming + st[i].math + st[i].physics;
avr=sum/3;
st[i].avr=avr;
printf("Average mark of %s is %.2f\n",st[i].name,st[i].avr);
}

}
void grade(){
for(int i=0;i<n;i++){
if(st[i].avr>100 || st[i].avr<0)printf("Impossible");
else if(st[i].avr>79 && st[i].avr<=100)printf("Excellent work\n");
else if(st[i].avr>59 && st[i].avr<=80)printf("Good work\n");
else if(st[i].avr>49 && st[i].avr<60)printf("Succeed\n");
else printf("you need to work hard\n");
}
}
void findbyname() {
bool j;
char name[10];
printf("The name you looking for : ");
getchar();
gets(name);
for(int i=0;i<n;i++){
if(strcmp(st[i].name,name)==0){
printf("these are %s Informations : \n",st[i].name);
printf("Id : %d",st[i].Id);
printf("\nMath: %.2f",st[i].math);
printf("\nPhysics: %.2f",st[i].physics);
printf("\nProgramming: %.2f",st[i].programming);
j=1;
}
if(j!=1){printf("\nDoes not exist");}
}
}
void findbyId() {
int j;
printf("The Id of the student you looking for : ");
scanf("%d",&j);
getchar();

Answer 1

//part2 of the code
void findbyId() {
int j;
printf("The Id of the student you looking for : ");
scanf("%d",&j);
getchar();
for(int i=0;i<n;i++){
if(st[i].Id ==j){
printf("These are student Informations with the Id : %d\n",st[i].Id);
printf("\nName : %s\n",st[i].name);
printf("Math: %.2f\n",st[i].math);
printf("Physics: %.2f\n",st[i].physics);
printf("Programming: %.2f\n\n",st[i].programming);
}
else if(st[i].Id !=j){ printf("Does not exist\n\n");}

}
}

void display(){
for(int i=0;i<n;i++){
printf("Student Id : %d\n",st[i].Id);
printf("Name : %s\n",st[i].name);
printf("Math: %.2f\n",st[i].math);
printf("Physics: %.2f\n",st[i].physics);
printf("Programming: %.2f\n",st[i].programming);
printf("Average mark of %s is %.2f\n",st[i].name,st[i].avr);

printf("\n\n");

}
}
void displaybygrade(){
int p;
int k=0;
for(int i=0;i<n;i++){
if(st[i].avr>=50){
printf("Student Id : %d\n",st[i].Id);
printf("Name : %s\n",st[i].name);
k++;
}
}
printf("the number of Students who succeed is : %d\n",k);
printf("\n\n");

}

void sup(){
int a;
printf("the Id of the Student you want to remove : ");
scanf("%d",&a);
for(int i=0;i<n;i++){
if(a==st[i].Id){
for(int j=i;j<n;j++)
st[j]=st[j+1];
n--;
}
}printf("the number of Students left is : %d\n",n);

}
void main(){
int choice;
bool i;
do{
printf("\n ============== Menu ===============\n");
printf("\t 1. Enter the student Informations\n");
printf("\t 2. Calculate the average\n");
printf("\t 3. Show the grade\n");
printf("\t 4. Search by student Name\n");
printf("\t 5. Search by student Id\n ");
printf("\t 6. Display students informations\n");
printf("\t 7. Display number of student

Answer 2

//part3
printf("\t 8. Delete students informations using Id\n");
printf("\t 0. exit\n");
printf("\n\n");
printf("Please choose an option :");
scanf("%d",&choice);
switch(choice){
case 1: storeinfo(); break;
case 2: avr();break;
case 3: grade();break;
case 4: findbyname();break;
case 5: findbyId();break;
case 6: display();break;
case 7: displaybygrade();break;
case 8: sup();break;
default: printf("Invalid Task");break;
}
printf("press(0) to exit");
scanf("%d",&i);
}while(i==1);
}

Answer 3

Lets say you place have the names of

Amine, Bob, Carlos, and David

findByName()

bool j; //not set, might be 0 or 1
…
//lets assume j = 0 this run
//assuming user input Carlos

for (int i = 0; i < n;i ++)

//loop 1
(strcmp(Amine,Carlos) != 0)

(0 != 1) print Does not Exist

//loop 2
(strcmp(Bob,Carlos) != 0 )

(0 != 1)print Does not Exist

//loop 3
(strcmp(Carlos,Carlos) == 0 )
print info
j = 1
( 1 == 1)

// loop 4
( strcmp(David,Carlos) != 0 )

(1 == 1 )

// end of for loop