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RSS订阅原创 Digital signature
Digital signatures are used to ensure the authenticity of message received. It uses asymmetric encryption.Sender:A message digest is a numeric representation of the content of a messageRecipient:About hash function:
2023-03-17 09:46:09
389
原创 Hexadecimal numbers
Why hexadecimal number are needed?When there is a need to display/write/read a binary number, we have to write/read/understand a bunch of 0s and 1s. It's tedious and error-prone.A hexadecimal equivalent of a binary number is much shorter. 4 bits are wr
2022-01-10 09:24:25
407
原创 Lossy VS lossless compression
Features in common:A compression algorithm is used The purpose is to reduce the size of data/files Less storage capacity will be needed to store the data/files Less time it will takes to transfer the data/fileDifferences:Lossy:some data will be r
2021-12-30 16:51:41
695
原创 The benefits of using relational database instead of file-based approach (AS).
Keyword: data redundancy, data privacy, data consistency, data integrity, data dependency,search & queryData redundancy: the same data stored more than once. It common that there are several copies of files so that the data can be shared to differen.
2021-12-27 09:01:17
274
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原创 What happens when you enter an URL in the address bar of your browser?
IGCSE computer scienceInternet technologies.
2021-12-18 20:56:40
1348
原创 Cookies
CookiesYou must have seen this when you were browsing a website: we use cookies to …. You have to accept the website policy and continue your browsing.Have you ever wondered what cookies are and what they are used for?CookiesCookies are packets o
2021-05-09 09:15:20
268
原创 CSMA/CD
CSMA/CDCarrier Sense Multiple access with Collision Detection It is a network protocol. It operates in the Medium Access Control (MAC) layer. Carrier Sense: it senses or listens whether the shared channel is busy or idle. It defers data transmission
2021-05-06 14:34:05
177
原创 How do digital cameras work?
How do digital cameras work?Lens is used to bring light to a fixed focal point. It directs light to a digital sensor. A CCD or CMOS, a photoelectric sensor, is used to convert the incoming light into digital image. A CCD or CMOS senser consists of thou
2021-05-05 16:01:21
154
原创 Issues that should be considered when using computers
Nowadays, more and more people use computer for work, communication, study and leisure. Computer and internet have changed the way we live dramatically. They make our work more efficiently and effectively, our lives easier. We can shop online, study online
2021-05-03 11:04:02
171
原创 IAS （Immediate Access Storage）
About IAS：IAS: immediate access storage.Read more at https://ictsmart.tripod.com/ict4/online/artstrr.htmRead more at https://www.ukessays.com/essays/information-technology/known-as-immediate-access-storage-information-technology-essay.phpThese two
2021-05-02 17:44:58
482
原创 What happens in a supermarket when a barcode is read at the checkout?
My bloghttps://blog.youkuaiyun.com/zhangxingping/article/details/116346886gives a detailed description of how a barcode scanner reads a barcode.This blog gives you a general description of what happens in a supermarket when a barcode is read at the checkout...
2021-05-02 10:20:31
132
原创 How does the barcode scanner read the barcode?
How does a barcode scanner read a barcode?A barcode is a seriesof dark and light parallel lines of varying thickness. The barcode scanner can produce light, red laser or red RED. The light is shined on the barcode when a barcode scanner is used to sca.
2021-05-02 09:04:26
191
原创 How does a key board work?
How does a key board work** 1. A keyboard has a key matrix and a microprocessor. **** 2.The key matrix is a grid of circuits underneath the keys.**** 3. The circuit for each key is broken at the point below the key. It like a switch. The switch is off.*
2021-01-08 09:01:09
176
原创 Bus and Star Topology
Bus and Star TopologyStar TopologyThe advantages of star topology:The disadvantages of star topology:Star TopologyThe advantages of star topology:If one link of the connections fails, the others will not be affected.Adding a new device to or removing
2020-07-01 14:22:56
1289
原创 Packet Switching vs. Circuit Switching
Packet Switching vs. Circuit SwitchingWhat is the Difference Between Packet Switching and Circuit Switching?新的改变功能快捷键合理的创建标题，有助于目录的生成如何改变文本的样式插入链接与图片如何插入一段漂亮的代码片生成一个适合你的列表创建一个表格设定内容居中、居左、居右SmartyPants创建一个自定义列表如何创建一个注脚注释也是必不可少的KaTeX数学公式新的甘特图功能，丰富你的文章UML 图表F
2020-06-20 10:54:22
1250
原创 BitTorrent
BitTorrentBitTorrent protocolKey termsBitTorrent protocolBitTorrent protocol is a peer-to-peer file sharing protocol. It works very differently from the traditional p2p files sharing protocol.Traditional file sharing protocol uses client-server model, w
2020-06-18 21:29:04
558
原创 Protocols
ProtocolsWhat is a protocol?TCP/IP protocol suiteWhat is a protocol?A protocol is a set of rules about the format of the messages exchanged between computers. The rules are agreed by both the sender and the receiver/recipient.TCP/IP protocol suiteTCP:
2020-06-13 08:43:12
943
原创 underflow, overflow, approximation and rounding error
Underflow, overflow, approximation & rounding errorWhat is underflow and what is overflow?Why may a floating-point representation be an approximation?What is rounding error?What is underflow and what is overflow?In computer science, real numbers are
2020-06-11 10:26:19
523
原创 File organization & File access
File organization & File accessFile OrganizationSerial file organizationSequentail file organizationSequential file organization with fixed-size recordsDirect-access (random access) file organizationMethods of file accessDirect-access file organization
2020-06-09 08:34:23
418
原创 User defined data types
Why are user-defined data types necessary?The build-in data types are not good/adequate enoughUser-defined data types make the program code more understandable and less error-proneWhat is a composite data type and what is a non-composite data type?A
2020-06-04 14:27:35
466
原创 HDD VS SSD
The following table shows the comparison betwee HDD and SSD.| |HDD| SSD||:–|Cost Not expensive/Cheaper (than SSD) More Expensive (than HDD)Capacity Larger capacity Usually smaller storage capacity, even though that there are large size SSD, over 1TB, b
2020-05-28 21:07:58
394
原创 Real-time streaming & on-demand streaming
Bit streamingNumbers, text, audio, video are all represented in binary form on computer. They are all represented by a bunch of 0s and 1s. Each 0 or 1 is called a bit. When there is a need to transmi...
2020-03-20 09:21:32
1028
原创 Recursion in computer science
What is recursion?In math, recursion is a common concept. It means that a function is defined in terms of itself. For example, the factorial function is defined:f(n) = n * f(n-1)f(0) = 1f(n) is de...
2020-02-19 11:56:58
182
原创 Possible ways in which malware can be introduced
The introduction of malware is associated directly with the activities of legitimate users of a system. Examples are:Attaching portable storage deviceFew decades ago, when internet was not a norm, ...
2020-02-10 16:51:54
233
原创 Computer Malware
A malware is a software that is designed to get on a computer and cause harms to the information there or problems with the way it works. Malware is the colloquial name for malicious software. Compute...
2020-02-09 22:46:16
415
原创 Computer mouse
The use of mouse became a norm with the creation of the Graphic User Interface. GUI introduced windows, menus, dialogs and other features to the User Interface (UI), which totally transformed the func...
2020-02-06 23:46:02
1045
原创 Stepwise Refinement
What is stepwise refinement?The verb refine means to improve a method, plan, system etc., gradually making slight changes to it. The word stepwise means to do something in a series of distinct stage...
2020-02-04 18:50:38
1000
原创 Video
Key pointsA video is simply a succession of still images/sequence of still images.Frame rate: the number of frames displayed per second, usually expressed in FPS.The resolution of a video is the n...
2020-02-03 17:34:08
513
原创 Input and output of sound
Key pointIn physics, sound is a vibration that propagates as an acoustic wave through a transmission medium, such as a gas, solid or liquid.In computer science, all type of information has to be in...
2020-02-01 14:19:31
340
原创 The internal operation of a laser printer
The core principleThe core principle is the physical law: opposite charges attract, like charges repel.Main componentsA drum, photoreceptor drum, photosensitive drumThe drum is coated with photos...
2020-01-31 22:25:55
290
原创 Digital Certificate
Previously, in digital signature, we mentioned that it is possible that an attacker may pretend to be someone else, generate the pair of keys, make a fake message, generate a digest using hash functio...
2020-01-31 13:58:31
1086
原创 Digital signature
In asymmetric encryption, the sender and the recipient, each has a pair of keys, a public key and a private key. The public key and private key are mathematically linked together. If a message is encr...
2020-01-30 23:19:22
774
原创 Symmetric encryption VS Asymmetric encryption
Encryption is a process of encoding the plaintext with a key to generate ciphertext so that the plaintext is unreadable. In such a way, the confidentiality of the original message is guaranteed.Decr...
2020-01-30 12:33:23
1032
原创 Fundamental encryption terms
Key Terms Plaintext:data before encryption. Ciphertext: the result of applying encryption algorithm to data. &...
2020-01-29 17:00:16
216
原创 Software engineering code of ethics recommended by ACM/IEEE
Software engineers shall commit themselves to making the analysis, specification, design, development, testing and maintenance of software a beneficial and respected professional. In accordance with t...
2020-01-28 12:01:44
609
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