- Question 1: Subroutines, macros, literals, variables, constants
The programmer while writing a program can also think about the future
work of a compiler. Certain solutions could be more suitable for the
compiler or the final machine language than some others.
- Give an example of a situation where routine XYZ would be better
to implement as a macro than as a subroutine.
- Give an example of a situation where routine XYZ would be better
to implement as a subroutine than as a macro.
Advantages? Disadvantages?
- Give an example of a situation where constant value X would be
better to implement as a literal than as a constant in the instruction.
- Give an example of a situation where constant value X would be
better to implement as a constant in the instruction than a literal.
- How does using a literal differ from using a variable? Advantages?
Disadvantages?
- How does using a literal differ from using constant field?
- Question 2: Name binding
Binding a name given in a program to its final value can occur at least
during the following phases: when program is written, during
compilation, during linking, during loading, during base register
loading, or during instruction execution time. When does the binding
occur for the following examples? Give reasoning.
| | Operation | Names |
| a. | add R1,ParX(FP) |
R1? ParX? FP?
ADD? |
| b. | XX dc 456789 | XX? |
| c. | call SP, IO.Print |
Print? |
| d. | DD equ 65 | DD? |
| e. | locX = 3456789; |
locX? variable of c language |
In each case, give reasoning why the binding can not occur sooner or later.
- Question 3: Duration of disk operations
Let us assume the following information about the disk system:
- The disk spins with speed 7200 rpm, it has one read/write head
per surface.
- There are 2000 cylinders (tracks per surface), each track
has 50 sectors, and a sector size is 0.5 kB.
- The seek time (head transfer time) is linear to the number of tracks
passed, and it is assumed to be 0.02 ms/track.
- The
location of each sector for one file is random, and from this one can
deduce (with probability theory) that the average number of tracks
passed is 667.
- The file is read
from the disk one sector at a time.
How long does it take, in average, to
read one 333.33 kB file? What about 24 MB file?
- Question 4: Linking
Linking. How would the Fig 7-15
(b) in Tanenbaum book [Tane99] change,
if the modules were linked (from bottom up) in order ACDB instead of the
order ABCD used in Fig. 7-15?
Please note that the addresses grow bottom-up in Fig. 7-15. Modules are
defined in Fig
7-14.
- Question 5: Memory mapped I/O.
In example
driver.k91 there is a device driver implemented with
direct I/O.
- How does the device driver know that the device has printed
the given number?
- What does the device driver do while the device is printing
the number? How long can this take?
- How does the device (device controller) tell the device
driver that the given task is done?
- How does the application program (that call the device
driver) know when the task given to the device is done?
- How should one modify the device driver, if one wanted to
use indirect I/O instead? The purpose is not to give a precise answer,
but just the general ideas on what needs to be changed in the driver in
case indirect I/O was used.
Are there any changes to
the specifications for the device (device driver) because of this
change?
Päivi Kuuppelomäki