Is it valid or allowed, can check if something is valid but sometime inacurrate
You can check if it is not correct.
This ensure data is correctly inputted and spots human errors.
Ensures data entered complies with allowable data
many different types of validation include:
type character checks presence checks
Is it the same?
It is a number that is derived from the other contents of the number
Backing up and archivivng
full compies every file fully]
Only copies files that are changed in the last backup
not the same as backup
storing old/unused data
Taking it from server mainframe
Transferring onto storage medium
Unlikely to be used again but still available.
Monday, March 9, 2015
- Missing extra brackets
- Using variables
- Brackets not used properly
- The statement in the code does not follow the rules of the language.
- Usually detected by the translator, as the statement cannot be understood.
- Programs will not be compiled
- The syntax of the code is correct
- the code does not do what it should
- Will usually run normally but with some unexpected result
- Usually tested while being tested
- Incorrect mathematical formulae
- Misplaced brackets
- Instruction written and therefore executed in the wrong order
Run time error
- The syntax is correct
- the logic of the program is correct
- extreme circumstances cause crash
- program attempts impossible operation
- causes program to crash at run time
- usually detected while testing
- Division by zero
- attempt to access non existent file
- attempt to reference array elements before they are initialised
Data which syhold genarate an error message
A set of rules that govern how something works.
Within a computer science:
- A communication protocol is a system of digital rules for data exchange within or between computers
- When data is exchanged through a computer network, the rules system is called a network protocol
Logical Protocol (SMTP) - It is how emails are sent
- HTTPS - Browsing through the net
Lowest layer is logical and the highest is physical.
Physical layer = Describes electrical and physical specifications for devices: Cable, connectors, hubs.
Data link layer = Provides connections between hosts on the same network: Ethernet
Network layer = Provides connection between hosts on different networks :IPv4 and IPv6. Routing of packets.
Transport = Provides transport of data: TCP and UDP. End to end connections.
Session = establishing a connection. Controls the dialogs between computers (handshake). Also controls duplexing termination and restarts.
Presentation = compressing the data. Provides a context for communication between layers
ASCII Characters, Encryption and decryption. Compression.
Application = HTTPS, where we find network application eg mail, browser
It hands communication between computers across networks.
- The scope of a declaration is the block of code where the identifier is valid for use
- A global declaration is made outside the bodies of all function and outside the main program. it is normally grouped with the other global declarations and places at the beginning of the the program file.
- Local declaration is one that is made inside the body of a function. locally declared variables cannot be accessed outside of the function they were declared in
- It is possible to declare the same identifier name is different parts of the program.
- We have used thus have been local variables
- A Local variable is a variable which is either a variable declared within the function.
- As you may have encountered in your programming if we declare variables in function then we can only use them within that function. This is a direct result of placing our declaration statements inside functions.
- A global variable def is a variable which is accessible in multiple scopes
- It is important to note that global variables are only accessible after they have been declared.
- Undisciplined use of global variables may lead to confusion and debugging difficulties.
- Instead of using global variable in function, try passing local variables by reference.