How to fix 'structuredfunctions not calling' - c

Question

So I wrote this code as a part of my assignment like so, we are still learning C language and I am just unable to correct this one. We have to make a code on writing a function to print the names of all the students that joined in a particular year.
It runs the code till switch case, but doesn't work further.
#include<stdio.h>
struct stdnt
{
char stName[100];
char stRNo[100];
char Dept[50];
char crse[50];
int YoJ[4];
}s[2];
void stYr(p)
{
printf("Student Name = %s\t",s[p].stName);
}
void stRNm(q)// q RNm
{
int i;
for(i=0;i<=1;i++)
{if(q == s[i].stRNo)
{
printf("Student Name = %s\t",s[i].stName);
printf("Student Year of Joining = %d\t",s[i].YoJ);
printf("Student Department = %s\t",s[i].Dept);
printf("Student Course = %s\n",s[i].crse);
}
}
}
int main()
{
int i;
int year;
int RNm;
int ch;
printf("Please Enter the details of 2 Students.\n");
for(i=0;i<=1;i++)
{
printf("Enter Name of Student %d:\n",i+1);
scanf("%s",s[i].stName);
printf("Enter Department of Student %d:\n",i+1);
scanf("%s",s[i].Dept);
printf("Enter Year of Joining of Student %d:\n",i+1);
scanf("%d",s[i].YoJ);
printf("Enter Roll Number of Student %d:\n",i+1);
scanf("%s",s[i].stRNo);
printf("Enter Course of Student %d:\n",i+1);
scanf("%s",s[i].crse);
}
printf("Enter 1 to Print the List of Student using Year.\nEnter 2 to Search the details of student using Roll no.\n");
scanf("%d",&ch);
switch(ch)
{
case 1:
printf("Enter the Year:\n");
scanf("%d",&year);
for(i=0;i<=1;i++)
{
if(year == s[i].YoJ)
{
stYr(i);
}
}
break;
case 2:
printf("Enter the roll number you want to search:\n");
scanf("%d",&RNm);
stRNm(RNm);
break;
}
return 0;
}
the question is
Create a structure to specify data on student given below : Roll number, Name, Department, Course, Year of Joining.
Assume that there are not more than 450 students (i am trying to code for 2 firstly will make it for 450 once it works)
also `
write a function to print name of all the students who joined in a particular year.
write another function to print the data of a student whose roll number is entered
make switch cases .
OUTPUT i am getting :
Please enter the details of 2 students .
Enter Name of Student 1:
katyal
Enter department :
Mech
Enter Year of joining:
2019
Enter roll number:
1
Enter Course :
C
Enter Name of Student 2:
Pranay
Enter department :
Mech
Enter Year of joining:
2019
Enter roll number:
2
Enter Course :
C
Enter 1 to Print the List of student using year
Enter 2 to print details of student using roll number
1
Enter the year:
2019
Process returned 0<0x0> execution time 30.600s
Press any key to continue.
Expected Output :
after the Year is entered after switch case, i expect the Function `stYr to get called and print the list of student with that Year as their Year of Joining
similarly if roll number is entered i want the details of that student printed.

Answer 1

As you're learning C code I think that you should start off by taking on board a few standard working practices.
It's very evident that either your teacher hasn't really coded in a working environment or they are expecting you to spot the mistakes.
I realise that there may be issues or restrictions due to your compiler, but here are some pointers that will help in future.
Here are some pointers based on your code.
Always initialise variables before use. If a variable can be null and that is not a valid value, check for null before use e.g. `char[] or pointer types.
Use typedef for structure declarations, this will allow the compiler to determine incorrect use through type checking during compilation.
Use long, meaningful variable and function names as an aid to understand the code.
Indentation with brackets e.g. { }, to make code easy to understand.
Refrain from using literal values in code as this can lead to introduction of bugs at a later stage if a value is not changed in all cases through the code.
Function parameters should be definitive in type - this makes code portable between compilers, environments and easier to understand.
In for loops try to only use less than < and greater than > comparisons.
In 'if' statements try to place non-assignable values on the left side as this will raise a compiler warning if you type = instead of ==.
Try and make functions re-entrant i.e. not reliant on global variables to determine their behaviour if possible, void func(void) should ring alarm bells.
Be careful when using signed values such as int use unsigned int in preference UNLESS you know that a variable will be assigned values of less than 0.
Declaring function parameters as const and then using local function variables as copies (if you wish to change their value) will make code easier to debug.
Switch statements should always include a default: to handle undetermined values.
struct stdnt /* REVIEW COMMENT: use typedef */
{
char stName[100]; /* REVIEW COMMENT: non-literal value for 100 */
char stRNo[100]; /* REVIEW COMMENT: Based upon later usage should this be unsigned int rather than char[] type */
char Dept[50];
char crse[50];
int YoJ[4]; /* REVIEW COMMENT: this is an array of int. Either use int or char[4] */
}s[2]; /* REVIEW COMMENT: separate out declaration for clarity and use a meaningful name */
I'd suggest that you change it to this
#define TEXT_LENGTH_LONG 100
#define TEXT_LENGTH_SHORT 50
#define NUMBER_OF_STUDENTS 2
typedef struct
{
char Name[NAME_LENGTH];
unsigned int RollNumber;
char Department[TEXT_LENGTH_SHORT];
char Course[TEXT_LENGTH_SHORT];
unsigned int YearOfJoining;
}student_t;
student_t students[NUMBER_OF_STUDENTS];
This function code has some issues.
void stRNm(q)/* REVIEW COMMENT: non-definitive declaration can cause confusion. Unclear function name and parameter */
{
int i;
for(i=0;i<=1;i++) /* REVIEW COMMENT: use of literal value makes maintenance more difficult and can introduce bugs if the array size is changed but this is missed */
{if(q == s[i].stRNo) /* REVIEW COMMENT: possible type mismatch in comparison - comparing int or char[] ?*/
{
printf("Student Name = %s\t",s[i].stName);
printf("Student Year of Joining = %d\t",s[i].YoJ);
printf("Student Department = %s\t",s[i].Dept);
printf("Student Course = %s\n",s[i].crse);
}
}
}
becomes
void PrintStudentInfo(const unsigned int rollNumOfStudent)/* Declaring rollNumOfStudent as const will give it compiler protection against being assigned to */
{
int i;
for(i=0;i<NUMBER_OF_STUDENTS;i++)
{
if(rollNumOfStudent == students[i].RollNumber)
{
printf("Student Name = %s\t",students[i].Name);
printf("Student Year of Joining = %d\t",students[i].YearOfJoining);
printf("Student Department = %s\t",students[i].Department);
printf("Student Course = %s\n",students[i].Course);
}
}
}
Okay this is just a start.
There are issues in your main function relating to what I've mentioned already that are causing the odd behaviour.
C is a language that is so loosely defined that it is very easy to introduce bugs due to shortcuts taken in coding.
Be pedantic.
Don't let the compiler make the decisions.
Be sure that the data types of variables are what you want rather than what the compiler determines.
Edit
Taking into account my comments about data types.
This line if(year == s[i].YoJ) is performing the following if(int == int[4])