Kareen IT theory book notes
IT Theory Notes
Chapter 1
*Advantages of encoding data:
1. So data can be stored and processed by a computer system
2. Reduce file size this will allow:
▪ Enables real time streaming of music and video
▪ Reduce file downloading time
▪ Less time to download media on website
▪ You can store more media on storage devices
3. Enables different formats to be used:
▪ PNG and GIF formats enable transparent backgrounds
▪ GIF allows animated images
▪ JPG allows very large colour depth
▪ BMP saves the image in the highest possible quality
▪ Formats that are designed for editing software allow adjustment
Disadvantages of encoding data:
1) Required codecs may not be installed so the files can’t be saved in the required format
2) Not all software is capable of opening different file types
3) Hardware may not be familiar with certain format so the media/ documents cannot be viewed/
played
4) Quality is lost due to lossy compression
5) Text that has been encoded using UNICODE may not completely work if international characters
were used if encoded to ASCII
,Kareen IT theory book notes
● *Encryption has three types:
1. Symmetric encryption: T his is the simplest kind of encryption that involves only one secret key to cipher and
decipher information. Symmetrical encryption is an old and best-known technique. The sender and the recipient should
know the secret key that is used to encrypt and decrypt all the messages
2. Asymmetrical encryption: is also known as public key cryptography.(most imp is to protect the private key very
well, since if stolen they can read any messages received but not sent)
● A person who wants to send a message/data to another person via the internet but securely (for example
bank account in online shopping) has to undergo the following:
1. The sender’s computer asks for the digital certificate of the recipient’s server/user this
dc has the organization name, organization that gave the dc, user’s email address
country and most importantly the public key
2. Both computers exchange public keys
3. The sender’s computer now encrypts the data/message using the public key
4. The recipient is the only one who can decrypt the message since (he/she)is the only one
that has the matching private key to that public key
3. Whole disk encryption: this is to prevent anyone from accessing files directly from the computer’s
hard disk or any other portable storage device because they are susceptible to loss and being stolen
this is usually done by adding biometrics or a password which is entered once you reboot your cs we
can add another layer of protection called TPM (a chip in motherboard)
● *Encryption protects data by only scrambling it and making it not understandable however it is still prone
to being tampered with ,stolen, or deleted
Caesar cypher (Shift Cypher): A type of cypher that select replacement letters by shifting along the
alphabet
, Kareen IT theory book notes
*Verification and validation
● Verification ensure:
o Accuracy of data
o Integrity of transmitted data
● Methods of verification:
o Double entry(D ocuments are typed in twice by different users then compared )
anually comparing original data with data entered)
o Visual Checking (M
o Data block verification(C hecked by computer following transmission, using checksum)
● Validation ensures:
o Data entered is reasonable
● Methods of validation:
o Range check
o Look up check
o Format check
o Length check
o Type check
● Validation doesn’t always work because:
o Data can be reasonable but not correct(that’s why we use both verif and valid)
IT Theory Notes
Chapter 1
*Advantages of encoding data:
1. So data can be stored and processed by a computer system
2. Reduce file size this will allow:
▪ Enables real time streaming of music and video
▪ Reduce file downloading time
▪ Less time to download media on website
▪ You can store more media on storage devices
3. Enables different formats to be used:
▪ PNG and GIF formats enable transparent backgrounds
▪ GIF allows animated images
▪ JPG allows very large colour depth
▪ BMP saves the image in the highest possible quality
▪ Formats that are designed for editing software allow adjustment
Disadvantages of encoding data:
1) Required codecs may not be installed so the files can’t be saved in the required format
2) Not all software is capable of opening different file types
3) Hardware may not be familiar with certain format so the media/ documents cannot be viewed/
played
4) Quality is lost due to lossy compression
5) Text that has been encoded using UNICODE may not completely work if international characters
were used if encoded to ASCII
,Kareen IT theory book notes
● *Encryption has three types:
1. Symmetric encryption: T his is the simplest kind of encryption that involves only one secret key to cipher and
decipher information. Symmetrical encryption is an old and best-known technique. The sender and the recipient should
know the secret key that is used to encrypt and decrypt all the messages
2. Asymmetrical encryption: is also known as public key cryptography.(most imp is to protect the private key very
well, since if stolen they can read any messages received but not sent)
● A person who wants to send a message/data to another person via the internet but securely (for example
bank account in online shopping) has to undergo the following:
1. The sender’s computer asks for the digital certificate of the recipient’s server/user this
dc has the organization name, organization that gave the dc, user’s email address
country and most importantly the public key
2. Both computers exchange public keys
3. The sender’s computer now encrypts the data/message using the public key
4. The recipient is the only one who can decrypt the message since (he/she)is the only one
that has the matching private key to that public key
3. Whole disk encryption: this is to prevent anyone from accessing files directly from the computer’s
hard disk or any other portable storage device because they are susceptible to loss and being stolen
this is usually done by adding biometrics or a password which is entered once you reboot your cs we
can add another layer of protection called TPM (a chip in motherboard)
● *Encryption protects data by only scrambling it and making it not understandable however it is still prone
to being tampered with ,stolen, or deleted
Caesar cypher (Shift Cypher): A type of cypher that select replacement letters by shifting along the
alphabet
, Kareen IT theory book notes
*Verification and validation
● Verification ensure:
o Accuracy of data
o Integrity of transmitted data
● Methods of verification:
o Double entry(D ocuments are typed in twice by different users then compared )
anually comparing original data with data entered)
o Visual Checking (M
o Data block verification(C hecked by computer following transmission, using checksum)
● Validation ensures:
o Data entered is reasonable
● Methods of validation:
o Range check
o Look up check
o Format check
o Length check
o Type check
● Validation doesn’t always work because:
o Data can be reasonable but not correct(that’s why we use both verif and valid)
