What is an Algorithm?

We saw above that planning a program involves defining its logic (the correct sequence of instructions needed to solve the problem at hand).The term algorithm is often used to refer to the logic of a program. It is step-by step description of how to arrive at the solution of the given problem. It may be formally defined as a sequence of instruction, designed in a manner that, if the instruction is executed in the specified sequence, the desired results will be obtained. In order to qualify as an algorithm, a sequence of instructions must possess the following characteristics:

1.    Each and every instruction should be precise and unambiguous.
2.    Each instruction should be such that it can be performed in a finite time
3.    One or more instructions should not be repeated infinitely. This ensures that the algorithm will ultimately terminate.
4.    After performing the instruction, that is, after the algorithm terminate, the desired results must be obtained.

Sample Algorithms

To gain insight in to algorithms, let us consider some simple examples

Examples:-

50 students in a class appeared in their final examination.Their mark sheets have been given to yo.The division column of the mark sheet contains the division(FIRST,SECOND,THIRD or FAIL) obtained by the student.Write an algorithm to calculate and print the total number of students who passed in FIRST  division.

Algorithm:-
Step:- 1  Initialize Total_First_Division and Total_Marksheets_Checked to zero.
Setp:- 2 Take the mark sheet of the next student.
Step:- 3 Check the division column of the mark sheet to see if it is FIRST.If no,go to Step 5.
Step:- 4 Add 1 to Total_First_Division
Step:- 5 Add 1 to Total_Marksheets_Checked.
Step:- 6 Is Total_Marksheets_Checked= 50? If no, go to Step2.
Step:- 7 Print Total_First_Division.
Step:- 8 Stop

Top 10 Tips-How To Protect your Computer

With Increased uses of the internet, there is a remarkable increase in online threats. It’s extremely crucial that you keep your computer safe from these threats. We are presenting 10 tips to keep your computer safe.

1. First and the foremost precautionary measure for keeping your computer safe is to invest in an antivirus program. Antivirus program will protect you from viruses and will help in avoiding any data loss or data corruption because of Virus infections. There is a new product line offered by all the Anitivirus vendors, called internet security. Internet security products protect you from antivirus, malwares and adwares.
2. Do not open suspicious email attachments. Many spam emails contain infected attachments. Make use of junk email filter and always block sender’s who send you infected emails.
3. Always install purchased software’s. Pirated software possesses threat and source files may be infected. Do not use keygens and cracks to activate pirated software’s.
4. Always scan email attachments, portable drives and CD/DVD media before copying data on your computer.
5. Do not download any suspicious files from websites, files with extensions like .scr, .vbs are executable files and are very common source of virus infection.
6. Always backup your data. This will help you to restore it in case your computer gets infected, and your data get corrupt. There are many online backup solutions available these days, which are cheap and easy to use.
7. Be aware of phishing emails. Such emails come from forged email addresses and often ask you to update your bank information or some other critical information like your email password. Information gathered using phishing emails can be exploited by the sender.
8. Use safe browsing practices. Install a pop-up blocker to disable advertisements, which lead to potentially dangerous sites. Keep your browser up to date to keep it secure, as many browsers these days release frequent updates to address the security issues. Keep your operating system updated with latest service pack and patches.

9. Do not share your personal information like phone numbers, bank details and passwords over messenger as many messengers do not encrypt the messages. The messages travel in plain text and can be hacked. Share sensitive data via email using encrypted email. There are some free encrypted email sending options available these days. Sendinc.com is one which is free and easy to use for sending encrypted emails.
10. Use a firewall on your computer and keep an eye on the traffic coming in, and going out of your computer. Block suspicious traffic. You can use hardware or software based firewalls. Windows come with an inbuilt firewall.

Tips on how to Speed up your Computer

Being a computer user, you always keep on finding ways to speed up your computers. Slow computer always results in spending more time in getting simple jobs done and results in low productivity. In many cases, the slowness is not related to computer hardware, it’s the junk and lack of organizing your stuff with the time that lead to slowness. We are presenting you 15 tips to speed up your computer.

1. Antivirus program: Always pay for an Antivirus program. If you cannot afford to go for a paid program, some of the top Antivirus Vendors like Avast and AVG provides a free Antivirus product, which is free for home usage. Viruses cause slowness and sometimes complete corruption of data on your computer. You risk everything if you do not have an antivirus program installed.

2. Unwanted Programs: Are you in a habit of downloading new programs and testing them? Every software you download and install for testing is taking up space, and in many cases it also modify the registry to run files at startup which eats your RAM. Make a habit to uninstall the programs you do not need.

3. Defragmentation: When you install a program or copy and save files on your computer the data is written to the closest available space and it results in fragmentation on your hard disk. Defragmentation process organizes the files on your hard drive and places the files together for faster access. You should defrag your computer frequently. There are many free utilities available to automate the process.

4. Disk Cleanup: If you are not a geek, Disk cleanup utility which comes free, with every version of windows can help you to cleanup junk files from your computer. You can find it under Startup Programs-> Accessories-> System tools.

5. Updates: Keep your system updates with latest patches. Keep your drivers updated. This will help you to run your computer at its optimum level. OS patches keep you safe from online threats and Virus infections. You can enable Automatic updates to update your system weekly.

6. Backup old data to External Drives: As External storage is cheap and very affordable these days, it’s always good to keep your old data on external storage and keep your computer free from unwanted or old data.

7. Upgrade Memory: Memory upgrade can give you significant boost. With Memory prices coming down, it’s always good to have more RAM in your system. More RAM helps in faster execution of programs.

8. Disable Startup Programs: To speed up the computer boot process, it’s always good to disable unwanted startup programs. You can do it by launching MSConfig utility.

9. Disable Indexing or Tweak the Indexing settings: Indexing files on your computer may result in slow performance. You should either disable Indexing or tweak settings so that indexing runs only when your computer is idle.

10. Multitasking: Depending on your computer hardware, you can run multiple programs up to a certain limit. Avoid using multiple instances of programs like Photoshop, illustrator, video editors and virus scanners at the same time.

11. Regular scanning: Schedule scanning your computer for any malware and adware programs. Malware and adware slow down your computer and sometimes result in frequent crashing of the application and computer.

12. You can use the sleep or hibernate mode to speed up the boot process.

13. Do not install unwanted Add-ons and themes

14. Do not browse potentially danger websites. Sites, which distribute pirated software’s and cracks are potentially dangerous sites and may infect your pc by exploiting vulnerabilities.

15. You can always use some tune up software’s like Advanced system care or Tune up utilities, these software’s scan your system and suggest you many tweaks, which you can apply with a single click to speed up your computer.

What is OS (Operating system)?

An operating system (often referred to as OS) is an integrated set of programs that controls the resources (the CPU, memory, I/O devices, etc) of a computer system and provides its users with an interface or virtual machine that is more convenient to use than bare machine. According to this definition, the two primary objectives of an operating system are:

1.       Makin a computer system convenient to use- An operating system is a layer of software on top of the bare hardware of a computer system, which manages all parts of the system, and presents to the user with an interface or virtual machine, which is easier to program and use. That is, the operating system hides the details of the hardware resources from the programmer and provides the programmer with a convenient interface for using the computer system. It acts as an intermediary between the hardware and its users, providing a high-level interface to low-level hardware resources, and making it easier for the programmer and other users to access and use those resources.

The logical architecture of a computer system is shown in figure………..

As shown in the figure, the hardware resources are surrounded by the operating system layer, which in turn is surrounded by a layer of other system software (such as compilers, editors, utilities, etc.)and a set of application programs(such as commercial data processing applications, scientific and engineering applications, entertainment and educational applications,etc).Finally, the end users view the computer system in term of the user interfaces provided by the application programs.

2.       Managing the resources of a computer system. The second important objective of an operating system is to manage the various resources of the computer system. This involves performing such tasks as keeping track of who is using which resource, granting resource requests, accounting for resource usage, and mediating conflicting requests from different program and users. The efficient and fair sharing of resources among users and/or program is a key goal of most operating systems.

Main Functions of an Operating System

The main functions performed by most operating systems of today are as follows:

1.       Process Management- The process management module of an operating system takes care of the creation and deletion of process, scheduling of various system resources to the different processes requesting them, and providing mechanisms for synchronization and communication among process.

2.       Memory Management- The memory management module of an operating system takes care of the allocation and deallocation of memory space to the various programs in need of these resources.

3.       File Management-The file management module of an operating system takes care of file-related activities such as organization, storing, retrieval, naming, sharing, and protection of files.

4.       Security – The security module of an operating system protects the resources and information of a computer system against destruction and unauthorized access.

5.       Command Interpretation – The command interpretation module of an operating system takes care of interpreting user commands, and directing the system resources to handle the requests. With this mode of interaction with the system, the user is usually not too concerned with the hardware details of the system.

In addition to the above listed major functions, an operating system also performs few other functions such as keeping an account of which users (or process) use how much and what kinds of computer resources, maintainance of log system usage by all users, and maintenance of internal time clock.

Measuring System Performance

The efficiency of an operating system and the overall performance of a computer system are usually measured in terms of the following:-

1.                               Throughput – Throughput is the amount of work that the system is able to do per unit time. It is measured as the number of process that is completed by the system per unit time. For example, if n processes are completed in an interval of t seconds, the throughput is taken as n/t process per second during that interval.Throughtput is normally measured in process/hour. Note that the value of throughput does not depend only on the capability of a system, but also on the nature of jobs being processed by the system. For long process, throughtput may be one process/hour: and for short processes, throughtput may be 100 process/hour.

2.                               Turnaround time – From the point of view of an individual user, an important criterion is how long it takes the system to complete a job submitted by him/her. Turnaround time is the interval from the time submission of a job to the system for processing to the time of completion of the job.Although, higher throughput is desirable from the point of view of overall system performance. Individual users are more interested in better turnaround time for their jobs.

3.                               Response time - Turnaround time is usually not a suitable measure for interactive systems, because in an interactive system process can produce some output early during its execution and can continue executing while previous results are being output to the user.Hence, another measure used in case of interactive systems is response time, which is the interval from the time of submission of a job to the system for processing to the time the first response for the job is produced by the system.

In any computer system, it is desirable to maximize throughput and minimize turnaround time and response time.

Related Post:-

What is Computer

Evolution of Computers

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The Evolution of computers

Necessity is the mother of invention. The saying holds true for computers also, because computers were invented because of man’s search for fast and accurate calculating devices.

The first mechanical adding machine was invented by Blaise Pascal in 1642.Later, in the year 1671; Baron Gottfried Wilhelm von Leibniz of Germany invented the first calculator for multiplication. Keyboard machines originated in the United States around 1880 and are extensively used even today. Around this period only, Herman Hollerith came up with the concept of punched cards, which were extensively used as input medium in computers even in late 1970s, Business machines and calculators made their appearance in Europe and America towards the end of the nineteenth century.

Charles Babbage, a nineteenth century Professor at Cambridge University, is considered the faster of modern digital computers. During his period, mathematical and statistical tables were prepared by a group of clerks. Even the utmost care and precautions could not eliminate human errors. Babbage had to spend several hours checking these tables. Soon he became dissatisfied and exasperated with this type of monotonous job. The result was that he started thinking to build a machine, which could compute tables guaranteed to be error-free. In this process, Babbage designed a “Difference Engine “in the year 1822, which could produce reliable tables. In 1842, Babbage came out with his new idea of Analytical Engine, Which was intended to be completely automatic. It was to be capable of performing the basic arithmetic functions for any mathematical problem, and it was to do so at an average speed of 60 additions per minute. Unfortunately, he was unable to produce a working model of this machine, because the precision engineering required to manufacture the machine was not available during that period. However, his efforts established a number of principles, which have been shown to be fundamental to the design of any digital computer. In order to have better idea of the evolution of computers, let us now briefly discuss about some of the well-known early computers. These are as follows:

1.       The Mark 1st Computer (1937-44. Also known as Automatic Sequence Controlled calculator, this was the first fully automatic calculating machine designed by Howard A. Aiken of Harvard University, in collaboration with IBM (International Business Machines).Corporation .Its design was based on the techniques already developed for punched card machinery. It was an electro-mechanical device, since both mechanical and electronic components were used in its design.

Although this machine proved to be extremely reliable, It was very complex in design and huge in seize. It used over 3000 electrically actuated switches to control its operations, and was approximately 50 feet long and 9 feet high. It was capable of performing five basic arithmetic operations: addition, subtraction, multiplication, division and table reference. A number as big 23 decimal digits could be used in this machine. It took approximately 0.3 second to add two numbers and 4.5 seconds for multiplication of two members. Hence, the machine was very slow as compared to today’s computers.

2.       The Atanasoff-Berry Computer (1939-42). This electronic machine was developed by Dr.John Atanasoff to solve certain mathematical equations. It was called the Atanasoff-Berry Computers, Or ABC,after its inventor’s name and his assistant, Clifford Berry. It used 45 vacuum tubes for internal logic and capacitors for storage.

3.       The ENIC (1943-46). The Electronic Numerical Integrator and Calculator (ENIAC) was the first all electronic computer. It was constructed at the Moore School of Engineering of the University of Pennsylvania, U.S.A by a design team led by Professor J.Presper Eckert and John Mauchly.

ENIC was developed because of military need, and was used for many years to solve ballistic problems, It took up the wall space in a 20*40 square feet room and used 18,000 vacuum tubes, The addition of two numbers was achieved in 200 microseconds, and multiplication in 2000 microseconds.

4.       The EDVAC (1946-56). A major drawback of ENIAC was that its program was wired on boards, which made it difficult to change the programs. This problem was later overcome by the “stored program” concept introduced by Dr.John Von Neumann. The basic idea behind this concept is that a sequence of instructions, as well as data, can be stored in the memory of the computers, for automatically directing the flow of operations. This feature considerably influenced the development of modern digital computers because of the ease with which different programs can be loaded and executed on the same computer. Due to this feature, we often refer to modern digital computers as stored program digital computers. The Electronic Discrete Variable Automatic Computer (EDVAC) was designed on stored both instructions and data in the binary form (a system that uses only two digits -0 & 1 to represent all characters), instead of the decimal numbers or human readable words.

5.       The EDSAC (1947-49). Almost simultaneously with EDVAC of U.S.A, the Bruisers developed the Electronic Deley Storage Automatic Calculator (EDSAC). The machine executed its first program in May 1949.In this machine, addition operation was accomplished in 1500 microseconds, and multiplication operation in 400 microseconds. The machine was developed by a group of scientists, head by Professor Maurice Wilikes, at the Cambridge University Mathematical Laboratory.

6.       The UNIVAC 1^st (1951). The Universal Automatic Computer (UNIVAC) was the first digital computer, which was not “one of kind”. Many UNIVAC machines were produced, the first of which was installed in the Census Bureau in 1951 and was used continuously for 10 years. The first business use of a computer, a UNIVAC 1^st, was by General Electric Corporation in 1954.

In 1952, the International Business Machines (IBM) Corporation introduced the 701 commercial computers. In rapid succession, improved models of the UNIVAC 1^st and other 700-series machines were introduced. In 1053, IBM produced the IBM-650, and over 1000 of these computers.

The commercially available digital computers, which could be used for business and scientific applications, had arrived.