Ms 2003 Ce Cs Paper Ibc C Version

Suggested Solutions to 2003 HKCEE Computer Studies Paper I Sections B & C (C Version) 7.

(a)

A check digit is an extra digit to validate a code / to check the correctness of a code

1

(b)

(i)

2

Values of i just after executing the for loop

n

sum

0

4

4

1

3

7

2

14

12

3

3

15

All correct for n: 1 mark All correct for sum: 1 mark (ii)

28 invalid card number

for ( i = 0; i < strlen(x); i++ ) if ( x[i] < '0' || x[i] > '9' ) flag = false; if ( !flag ) printf("Digits from \"0\" to \"9\" only!\n");

(c)

(d)

(1) (2)

if ( sum % 10 == 0 ) printf("Calculated check digit is 0\n"); else printf("Calculated check digit is %d\n", 10 - (sum % 10));

1 1 1 1 1

OR: printf("Calculated check digit is %d\n", (10 - (sum % 10)) % 10); 8.

#include <stdio.h> int main() { int NUM, COUNT, LOWER, UPPER; scanf("%d %d", &LOWER, &UPPER); NUM = LOWER; while ( NUM <= UPPER ) { COUNT = 2; while ( (NUM % COUNT) != 0 ) COUNT++; if ( NUM == COUNT ) printf("%d\n", NUM); NUM++; } return 0;

2

1 1 1 1 1 1 1 1 1 1

} 9.

(a)

char* secret fopen “r” feof(fp)

(b)

void init() { for ( i = 0; i < strlen(secret); i++ ) solution[i] = '*'; solution[strlen(secret)] = '\0'; noOfAttempts = 2 * strlen(secret);

2003-CE-COMP STUD 1B & C-1 (C Version)

0.5 0.5 0.5 0.5

1 1

} (c)

void letterGuess() { char inp[80]; printf("Please input the letter you guess: "); scanf("%s", inp); letter = inp[0]; for ( i = 0; i < strlen(secret); i++ ) if ( letter == secret[i] ) solution[i] = letter; printf("%s\n", solution); noOfAttempts--; printf("No. of attempts remaining = %d\n", noOfAttempts);

1 1 1 1

} (d)

10.

void winCheck() { if ( strcmp(solution, secret) == 0 || noOfAttempts == 0 ) done = true; }

1 1

(a)

trackball, touch screen, touch pad, trackpoint, joystick (any two)

1+1

(b)

(i)

Smart cards can be lost / counterfeited / stolen.

1

(ii)

fingerprint recognition voice recognition retina recognition (any two)

1+1

(i)

They want to withdraw / deposit cash.

1

(ii)

It is more secure.

1

(i)

ATM kiosk 4 and ATM kiosk 6

(ii)

optical fiber (fibre) / twisted pair / UTP (any one)

1

(iii)

Data sent across the data line is encrypted (encoded) into unreadable strings of messages.

1 1

The coded strings of messages are decrypted (decoded) at the receiving end.

1

(c)

(d)

(e)

Once the database in a district computer is updated, messages should be sent to other district computers for synchronizing the copies of the database. (update the databases in the other computers)

2

(f)

Customers will spend more time at the ATM kiosks in waiting the process. (loading) If the district computer C is out of order, all ATM kiosks cannot be operated. (reliability)

2 2

Effective communications: Relevance

0 / 1 /2

Language/Style correct and appropriate

0/1/2

0/1/2/3/4

2003-CE-COMP STUD 1B & C-2 (C Version)