Lecture 8 Flashcards
Computers cannot run programs expressed with names, they need ot translate the version with names to _______ ______
machine code
The translslator from code we can understand to machine code is _____
assembler
____ _____ is the discipline devoted to best practices in design and
building of programs
software engineering
What are some of the programming best practices
- Write code that is clear and easy to understand
- Comment the code
- Effective use of white space
- Use built-in constants
What are the key features of programming
Human readable -Loop -Conditionals (If, then, else) -Simple operations (Give flexibility instead of hard coding)
The source code to assembler or machine code is called:
- Compiler if translation done completely before program loaded to run
- Interpreter if translation is done statement by statement as program runs (like DOS based Basic)
A Program exists as disk file called a _____ _____
that contains _____ _____
- load module
- executable code
_____ _____ is software in a form that can be run on a computer. It typically refers to machine language
Executable code
A _____ loads the load modules into memory
loader
A ____ job is to resolve undefined references in code by linking library object code with our newly created object code
linker
What are the different kinds of load modules
- Absolute Loading
- Relocatable Loading
- Dynamic Run-Time Loading
What is the problem with absolute loading
associated (bound ) a real memory address to variables, targets at compile
time
What is the problem with relocatable loading?
associated (bound) a real memory address to variables, targets at load
time (can’t swap)
Dynamic run time loading works by
delay that association (binding) until run-time (requires DAT)
There are two ways to link .
Static: Appended to generated code
Dynamic: called at either load time or run time.
Magnetic disk
Have > 1 disk coaded with magnetic material (mylar or aluminum)
Disk rotates on center axis
Head is fixed onto arm
How much does each sector hold?
512 bytes of data
Hard disk can have multiple ____ per spindle
Platters:
and use both top and bottom surfaces of each platter
with multiple heads between platters
Data rate of 3600 RPM disk is:
- 80 Mbytes per second (per surface)
- But head has to be in right place
Move a disk ____ is called a see
head
What is the average latency to access data:
average seek time + average rotational delay
There are two types of disk spin we need to be aware of:
- Constant angular velocity disc (track size decreased towards center)
- Constant linear velocity disc (track size constant)
Solid state disk remove two delays
rotational delay and seek delay are both gone
Solid state disk suffer from the fact that cells can’t be overwritten instead you must
Write new data to new sector than erase old data (garbage collection)
What are the two main standards today for disk controller
SCSI and SATA
The operating system does not talk directly to disk, instead it talks to ____
controller
