Cambridge IGCSE and O Level Computer Science Second Edition

Data may be corrupted, lost, or even gained.

A method of data transmission in which a message is broken up into packets that can be sent independently.

Computers cannot understand corrupted text, making error checking essential.

0 1 0 1 1 1 0 0.

To reassemble packets into the original sequence.

To facilitate reassembly of the data at its destination.

The checksum is recalculated and compared to the transmitted checksum.

By re-calculating the parity of the received byte.

The same key is used for both encryption and decryption.

It shifts letters in a word across the alphabet by specific amounts.

IP addresses of sender and receiver, packet size, sequence number.

If the remainder from division by 10 is zero, that is the check digit; otherwise, subtract the remainder from 10.

The actual data being sent, usually about 64 KiB.

Keeping the encryption key a secret.

Parity checks, checksum, echo check.

Universal Serial Bus.

ISBN 13.

Add all the odd numbered digits together.

The parity bit, usually the most significant bit.

To provide a check against errors in the transmitted data.

To limit the number of routers a packet can traverse before being deleted if it hasn't reached its destination.

Multiply each digit by its weighting, sum the values, divide by 11, and check if the remainder is zero.

A method used to check if data has been changed or corrupted following data transmission.

Data can be sent in one direction only, like from a computer to a printer.

A method where data is sent back to the sender for comparison to check for errors.

Because each packet can take its own independent route in the network.

A method where several bits of data are sent down several channels/wires simultaneously.

Credit card or bank details.

Each worker needs to generate their own matching public and private key pair and exchange their public keys.

An encrypted message.

To enable secured encrypted communication between them.

Another method of sending packets that differs from packet switching.

It becomes impossible to know exactly which bit is in error without additional methods.

The receiving device sends a negative acknowledgement and requests re-transmission of the data.

To correct the error and ensure accurate data transmission.

Routers receive data packets and determine their next route based on the header information.

To check whether data has been changed or corrupted following data transmission.

Even parity and odd parity.

It works well over long distances and data arrives fully synchronized.

They may select the shortest available path, considering congestion at different nodes.

Data is sent multiple bits at a time over multiple wires/channels.

Yes, serial data transmission can be any of these types.

A change in parity from even to odd in any row or column.

Data can be sent in both directions simultaneously.

Another name for a hacker who intercepts data being transmitted over a network.

The actual data being carried in a data packet.

An encryption key that is known only to a single user or computer.

To minimize the risk of data interception by eavesdroppers.

Data can be sent in both directions but not at the same time, like a walkie-talkie.

An even number of 1-bits.

It may be impossible to locate the error using parity checking.

Add odd digits, multiply the sum of even digits by 3, and combine the results to find the check digit.

To identify not only that an error has occurred but also where it is located.

It totals the number of 1-bits horizontally and vertically to check for errors.

To identify the end of the packet and provide error checking.

Because distances are short and high-speed transmission is essential.

It has fewer hardware requirements.

The end of the data packet and includes the cyclic redundancy check (CRC) for error checking.

A type of encryption where the same key is used for both encrypting and decrypting a message.

It notifies the transmitter to re-transmit data if errors are detected.

An odd number of 1-bits at the receiver's end.

By adjusting the incorrect bit according to the parity check.

Ciphertext.

It is not very reliable as it's unclear when an error occurred during the original or returned transmission.

It allows the use of a public key for encryption and a private key for decryption, eliminating the need to share a secret key.

She can exchange it with anyone to receive encrypted messages that can be decrypted with her private key.

To ensure packets can be reassembled in the correct order.

It is the reverse of encryption with each letter shifted by a negative value.

Plaintext is readable data, while ciphertext is unreadable data after encryption.

It can have skewed bits due to multiple channels.

Even parity bit is 1, odd parity bit is 0.

Data is sent one bit at a time in one direction only.

Cyclic Redundancy Check (CRC).

Making data meaningless using encryption keys, which cannot be decoded without the correct decryption key.

A type of encryption that uses public and private keys to secure data.

Data that can be sent in both directions simultaneously.

To identify errors in data entry caused by mis-typing or mis-scanning a barcode.

Odd parity.

Serial data transmission.

To verify that the 13-digit code is correct.

Even parity.

To 0 if there is already an even number of 1-bits in the byte.

To 1 if there is already an even number of 1-bits in the byte.

An agreement between sender and receiver about which type of parity is being used.

1, since it should have an even number of 1-bits.

By comparing the number of 1-bits in the payload between sender and receiver.

It ensures that even if the public key is shared widely, only the owner of the private key can decrypt messages.

The time interval allowed to elapse before an acknowledgement is received.

Because the private key is required for decryption.

Encrypted data resulting from applying an encryption algorithm to plaintext.

Compatibility issues with older versions.

The sentence with jumbled letters: 'Can you raed tihs?'

It is split up into several packets before being sent.

Entering 5037 instead of 5307.

Jane needs to generate her own public and private key pair and share her public key with Tom.

Checksum.

Add the results of odd and even digit sums and divide by 10; the number is correct if the remainder is zero.

Generating and verifying check digits for varying lengths of numbers, such as product codes or VINs.

Assign each digit a weighting from 8 to 1 starting from the left.

Public key and private key.

Data is sent one bit at a time in one direction only.

To encrypt and decrypt messages securely.

100 watts (20 volts).

Data is transmitted one bit at a time.

Data that can be sent in both directions but not at the same time.

Header, Payload, Trailer.

It recognizes the first and last letters, but not every letter individually.

Incorrect digits, transposition errors, omitted or extra digits, and phonetic errors.

The destination IP address and the number of packets waiting at each node.

No need to tie up a single communication line, overcoming failed lines, easy expansion, and high data transmission rates.

The final digit in a code calculated from all other digits in that code.

Parallel transmission sends multiple bits at once, while serial sends one bit at a time.

Apply the same decryption key.

It converts it into an unreadable form (ciphertext).

Data can become skewed, arriving unsynchronized or out of order.

Subtract the remainder from 11.

To verify that data has arrived at its destination unchanged.

Approximately 1.2 × 10^77 combinations.

False.

Moves data packets between different networks, such as connecting a LAN to a WAN.

Sending data down several channels/wires several bits at a time.

Interference, problems during packet switching, and skewing of data.

Using an agreed algorithm from the block of data before transmission.

If the recalculated checksum matches the transmitted checksum.

An error message asking them to re-transmit the block of data.

Data is sent one bit at a time over a single wire/channel.

Packets can be lost, prone to errors in real-time streaming, and delays while re-ordering packets at the destination.

Packets may keep 'bouncing' around from router to router without reaching their destination.

The computer automatically detects the device and loads the appropriate driver software.

The packet is deleted when it reaches the next router.

The check digit is represented by 'X'.

The number is considered correct.

Her private key.

The time interval allowed to elapse before receiving an acknowledgement.

It automatically re-sends the data until a positive acknowledgement is received or a pre-determined number of re-transmissions has been reached.

True.

The transmission of data over a network for live events where data is sent as soon as it is received.

An odd number of 1-bits.

Three 1-bits (odd parity).

A method of data transmission where packets are sent over various paths and reassembled at the destination.

Half-duplex and full-duplex.

They need to be reassembled into their correct order using the header information.

Data.

A hacker who intercepts data transmitted over a network.

Over short distances.

Serial.

0, since it should have an odd number of 1-bits.

A method of checking transmitted data for errors, using acknowledgement and timeout to request re-sending of data if no acknowledgment is received in time.

USB-C.

To check if data has been transferred correctly by sending data to a receiver and immediately getting it sent back for verification.

10 gigabits per second (10 Gbps).

An error checking method that adds all 1-bits in the data packet payload and stores the total in the packet trailer.

An encryption key that is known to all users.

A method used to check if data has been transferred correctly, using even or odd parity.

Plaintext.

Data can be sent in both directions simultaneously, like in a broadband internet connection.

It ensures that the number of 1-bits in a byte is even.

For power supply.

In barcodes, such as International Standard Book Numbers (ISBN) and Vehicle Identification Numbers.

Simplex, half-duplex, or full-duplex.

Serial has less risk of external interference than parallel.

A request to re-send the missing packets.

Byte 8 (row 8) and Bit 5 (column 5).

The packet needs to be re-sent.

The IP addresses of the sender and receiver, along with the packet number for reassembly.

The original text/message before it is encrypted.

Standard USB only supports a maximum cable length of 5 meters.

A verification method used to check if transferred data has been altered or corrupted, calculated from the data block.

It can miss identifying errors if the byte retains even parity despite being corrupted.

Add all the odd-numbered digits together, including the check digit.

It transmits data at a slower rate.

There is an error in that byte.

Parity bits produced by the vertical parity check, indicating the end of the data block.

Cyclic Redundancy Check (CRC).

Each worker must swap public keys with all others.

A message sent to the sender indicating that data has been received correctly, used in the ARQ error detection method.

The key distribution problem.

Yes, with USB 2.0 and 3.0 using a suitable adaptor.

Stages in a network that can receive and transmit data packets; routers are examples of nodes.

A computer capable of performing fast calculations based on probability, potentially processing more data than traditional computers.

They use their private keys to decrypt information sent to them.

Each digit is multiplied by its weighting, summed, divided by 11, and the remainder is used to find the check digit.

24 pins.

Mobile phone networks to guarantee data integrity.

A method of transmission where a message is broken into many data packets sent independently along different pathways.

USB data transfer rates are slower compared to Ethernet.

It is made available to everybody for encrypting messages.

It uses positive and negative acknowledgements to indicate if data has been received correctly.

A small part of a message/data transmitted over a network, which can be reassembled at the destination.

5 meters or less.

Data that can be sent in one direction only.

An additional digit appended to a number to verify if the entered number is error-free.

Sending 8 bits of data at a time.

Sending data down one channel/wire one bit at a time.