2019-2020-1 20175320 "Information Security System Design Basics" fourth week of learning summary
First, the learning content summary
This week we learned about the representation and method for processing information in a computer system, including the following three aspects: binary conversion, bit the concept and operation, and represents information, numerical computation and storage of information.
Hexadecimal conversion
Base conversion has been mentioned many times in front of the doors of course, I will not repeat them here.
The concept of position
This section introduces the concept of bit vector, and introduced bit arithmetic and logical operations, and introduce two shift mode, this portion should be noted that:
- Note that the symbol bit arithmetic and logic operation symbol differences and the differences between the results of the data type.
- A shift operation is divided into logical shift and arithmetic shift, must be familiar with both signs. Zero padding logical shift, arithmetic shift complement sign bit, and therefore more arithmetic shift right that is used in the case of the division number of symbols.
Presentation of information
In this section explains the concept of complement, and proposes the concept of conversion between the unsigned number notation as well, and binary encoding with the unsigned and signed numbers, the IEEE standard describes how floating point numbers and how converted to decimal. This part should be noted that:
- In the conversion of the number of textbooks are several functions using abstract symbols represent, such as "B2Tw", which requires us to be familiar with each function symbol meaning of the expression.
- We must see the data to be converted using the conversion formula in a range no data, and the data is within the range of what belongs.
- Note, in particular in the c language, to include both signed and unsigned number of expression, in the calculation process c language Symbol Parameter forces will have converted to unsigned number, for the logical operation expression, this approach It will lead to non-intuitive result of the operation.
- Binary to decimal floating-point conversion process, the exponent E is reflected in the weights, it reflects part of the mantissa M after the decimal point calculation process in the formula, the exponent field, and a fraction field to be converted to Decimal.
- Floating point rounding further relates to the problem, chapter describes the four rounding method, when it is desired rounded number rounded result is an intermediate value, the need to use the even rounding mode.
Numerical computation
The main operation is carried out for unsigned and signed numbers in both cases, be noted that:
- In this chapter division is divided by a power of 2, unsigned results may be obtained directly through a logical shift, there is the need to add the number of offset symbols after arithmetically shifting the result obtained.
- Using complement multiplication, the code needs to be converted into complement signed numbers, using a signed number is calculated after the results of the calculation result into complement, if the overflow bit is required to exceed the length of the truncated, then the remaining conversion of complement signed numbers.
Store information
This section introduces the big end and the small end of storage of the two types of computers, and to understand the function between several network host endian byte order conversion.
Second, the problem of teaching and learning in the process of resolving
Problems encountered in this chapter basically solved by reading textbooks and Internet search, I noticed the problem after the contents EDITORIAL partial solution.
Third, the problem of debugging the code and resolution
This week is mainly theoretical content, not the amount of code, during the operation and did not encounter problems, the following is the code run results screenshot.
Fourth, code hosting
Fifth, last week summed up the wrong title examination
One problem:
One problem resolved: TEMP local variables do not appear in the symbol table.
Second problem:
Second problem resolved: gcc -g appear .debug .line
Six other (perception, thinking, etc., optional)
This week's task compared to last week's task less practical operation, many more theoretical knowledge. In this chapter, I understand the message data is stored in the computer and c language is how to convert these data and operations, by understanding these basic theories, so I have more understanding of the laws of the computer system running so that I can find some previously not aware of the error caused by the operation of law system in the programming process. Although this chapter is more complicated, but I think these elements allow us to think more rigorous, from another point of view to solve the problems encountered in the program.
Seven, learning progress bar
| The number of lines of code (add / accumulate) | Blog amount (add / accumulate) | Learning time (add / accumulate) | Important growth | |
|---|---|---|---|---|
| aims | 5000 rows | 30 | 400 hours | |
| the first week | 54/54 | 1/1 | 13/13 | |
| the second week | 59/113 | 1/2 | 22/35 |
Try recording "planned learning time" and "actual learning time" to the end see if you can improve their ability to plan. This study is very important work, is also useful. Consuming an estimated equation: Y = X + X / N, Y = XX / N, training more often, X, Y will close.
Reference: Why is estimated that software engineering software so hard , software engineering estimation method
- Plan study time: XX hours
- The actual study time: XX hours
- Improvements:
(Available see more modern software engineering courseware software engineers the ability to self-evaluation form )