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Defining a record data type and declaring a record Array of records

Defining a record data type and declaring a record Top

In C++, records are called structures. We can use the reserved word struct to define a record data type and declare a record type variable:

struct StudentRecord {             // Defining a record data type to store student's info
  char student_no[8];              // 1st field: Student Number
  char name[20];                   // 2nd field: Name
  char class_name[3];              // 3rd field: Class
  int class_no;                    // 4th field: Class Number
};

struct StaffRecord {               // Defining a record data type to store staff's info
  char employee_no[6];             // 1st field: Employee Number
  float salary;                    // 2nd field: Salary
};

struct StudentRecord a_student;   // a_student is a student record variable
struct StaffRecord an_employee;   // an_employee is a staff record variable

Usually, we use typedef to define a record data type for convenience:

C++ version Equivalent Pascal version

typedef struct StudentRecord {
  char student_no[8];
  char name[20];
  char class_name[3];
  int class_no;
} StudRec;

typedef struct StaffRecord {
  char employee_no[6];
  float salary;
} StaffRec;


StudRec a_student;
StaffRec an_employee;		 type
  StudRec = record
              student_no: string[8];
              name: string[20];
              class_name: string[3];
              class_no: integer
            end;

  StaffRec = record
               employee_no: string[6];
               salary: real;
             end;

var
  a_student: StudRec;
  an_employee: StaffRec;

The syntax for referring a field of a record in C++ is the same as that in Pascal: using a dot (.). For example, according to the above record definitions, an_employee.salary refers to the field salary of the record an_employee.

Array of records Top

Declaring an array of record is similar to declaring an array of simple data types. For example, according to the above record definitions, the following statement declares two arrays of records:

StudRec students[1500];    // an array of 1500 student records
StaffRec staff[100];       // an array of 100 staff records

The following sample program outputs all students with surname "Chan":

Program 27: Using an array of records
C++ version Pascal version
#include <iostream.h>
#include <string.h>
#define MAX 5
main()
{
  typedef struct StudentRecord {
    char student_no[8];
    char name[20];
  } StudRec;

  StudRec students[MAX];
  int i;
  char s[20];

  for (i = 0; i < MAX; i++) {
    cout << "Student " << i << ":\n";
    cout << "Student Number: ";
    cin.getline(students[i].student_no, 8);
    // The above statement reads a string
    // of maximum length 8 into the variable
    // students[i].student_no.
    cout << "Name: ";
    cin.getline(students[i].name, 20);
  }

  for (i = 0; i < MAX; i++) {
    strncpy(s, students[i].name, 4);
    s[4] = '\0';
    if (strcmp(s, "Chan") == 0)
      cout << students[i].name << endl;
  }
  return 0;
}		 program prog_27(input, output);
const
  MAX = 5;

type
  StudRec = record
              student_no: string[8];
              name: string[20]
            end;
var
  students: array[0..MAX - 1] of StudRec;
  i: integer;
  s: string[20];
begin
  for i := 0 to MAX - 1 do begin
    writeln('Student ', i, ':');
    write('Student Number: ');
    readln(students[i].student_no);
    write('Name: ');
    readln(students[i].name)
  end;

  for i := 0 to MAX - 1 do


    if copy(students[i].name, 1, 4) = 'Chan'
      then writeln(students[i].name)
end.
Sample output (text in red is entered by user):
Student 0:
Student Number: 123456
Name: Chan Chi Ming
Student 1:
Student Number: 475721
Name: Lam Wai Ming
Student 2:
Student Number: 134578
Name: Chan Kin Wing
Student 3:
Student Number: 721535
Name: Chan Lai Sheung
Student 4:
Student Number: 127310
Name: Man Chi Wah
Chan Chi Ming
Chan Kin Wing
Chan Lai Sheung

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