Other models are acceptable as long as they emphasize the cyclical nature of the problem-solving process.

Examples are: interviewing current users and domain experts, constructing questionnaires, observing current systems and studying prospective user-based documentation.

This may include: a definition of inputs and outputs, a list of tools, facilities, people available for developing the solution, and a schedule for the next stages of the project.

A feasibility report may be produced during the analysis phase, the design phase, or both. It may include: a brief description of the proposed system; estimated costs; economic, technical and legal responsibility; and a possible completion date.

Several possible solutions should be considered and evaluated by asking questions such as: What kind of output should be produced? Where will the input data come from and how will it be entered? Should the system be centralized or networked? Should computers be used at all? Should standard software packages be used? How much customization is desirable? The emphasis should be on modular organization. The human–computer interface should be considered.

Students must be able to propose suitable test data, with reasons, during the design and implementation stages.

Methods include: running old systems in parallel with new systems, direct changeover and phased introduction. Training implications and possible disruption during installation should be considered.

Features to be considered include periodic reviews, performance evaluation and clear documentation, to facilitate modifications.

Students should realize that activities such as interviews, questionnaires and literature searches are required to discover the relevant aspects.

For example, the modules might represent the input, process and output of the solution to the problem.

Symbols that students should use appear in appendix 3.

See 1.1.8 for installation methods to be considered.

The social significance must be treated by reference to economic, political, cultural and environmental consequences. These include: effects on employment (resulting in changes to the working environment, retraining and so on); computers (hacking, viruses and so on); ethical and legal requirements; data storage (preserving privacy, data protection and so on); software users (copyright, software licensing and so on).

One model includes: systems analysis, leading to a precise statement of the problem that needs solving (a requirements specification); software design; program construction, including testing and debugging; installation and operation; and maintenance. Other models are acceptable, as long as they emphasize the cyclical nature of the life cycle.

Students should understand that computer systems are used over long periods of time. The software in these systems requires periodic improvement. After the original design and implementation, further analysis, redesign and restructuring are required to accommodate changing needs. This will continue through many cycles of analysis, design, implementation and use.

Prototyping can be done at many levels of sophistication. For the purposes of this course prototyping is limited to the presentation of a preliminary solution that may not be functional.

Prototyping can be used with end-users for the purpose of obtaining feedback at an early stage in the design process. Prototyping can be used by systems designers to investigate alternative solutions to a problem.

Only a qualitative treatment or a specific calculation is expected; “O” or BigO notation is required only at HL. (See 5.6, Algorithm evaluation.)

Testing implies tracing sections of an algorithm, including responses to errors (“dry runs”), as well as the design of test cases, which are then executed. Students must be able to propose suitable test data, and give reasons. Debugging has the components of detecting, diagnosing and correcting errors shown up by testing.

Ideally, students should use an integrated development environment (IDE) combining an editor, interpreter or compiler and debugging tools, but this is not a requirement.

Students are required to document their problem-solving process according to the standards described in the guidelines for program dossiers. Program listings must also be thoroughly documented.

Students are required to write end-user instructions according to the standards described in the guidelines for the program dossier. Students should know that other user manuals may be needed (for example, on-line help systems and installation manuals where systems are installed by personnel other than end-users), but they are not required to write such documentation.

The translators should be limited to interpreters and compilers.

Examples include: database management systems, macros, CASE tools and simple language translators (interpreters and compilers are not suitable examples in this context), HTML editor, web page editor, code editor, visual IDE.

Students are expected to be able to reproduce a basic diagram illustrating the CPU and to know that each location in primary memory has a unique address.

Students must understand that everything in a computer is held and processed in binary, hence the relation between bits, bytes and so on in powers of 2. For example 1 kilobyte = 2^10

They should be familiar with the prefixes T, G, M, k and their use in computer science measure. They must be able to apply the prefixes T, G, M and k to bits and bytes. For example TB (terabytes), Gb (gigabits), MB (megabytes).

The study of specific registers is not required.

A single processor model is sufficient. The study of a specific CPU is not required.

Students must understand the function of RAM, ROM and cache memory and their typical sizes (in bytes). The way in which virtual memory can be used to expand primary memory must be understood but details of paging are not needed.

Secondary memory should refer to flash memory disks, CDs and DVDs and tape. Students must know the type of access of the above secondary memory media. They should also be able to give an application of each type and justify its use for this application.

The need for different types of memory in a microprocessor must be understood. Students must be able to quote at least one example of the use of a microprocessor and state the inputs and outputs.

Students must know the following features: mouse, keyboard, touch screen, optical character recognition (OCR), magnetic ink recognition (MICR), scanners (page, mark sense and barcode), LCD panels, speech recognition, sensors, digital cameras, graphics tablets, printers, plotters, monitors, robotics, sound. Technical details are not required unless introduced in the case study.

Technical details are not required unless introduced in the case study.

Knowledge of specific operating systems is not required.

Functions include: communicating with peripherals; coordinating concurrent processing of jobs; memory management, resource monitoring, accounting and security; program and data management; providing appropriate user interfaces.

The terms multi-access and multi programming should be understood but details of the way in which they are managed will not be examined.

Personal computers, portable computers, mainframes and supercomputers should be considered. Characteristics must include: primary and secondary memory size; input/ouput (I/O) devices; environment (size, convenience, where it is used); cost, users (multi- or single-); and processor (word length, bus size and frequency).

This should relate to the examples in 3.3.6.

The need for, and use of, backing-up strategies, mirrored systems and the utilities in 3.7.

Students must be able to explain and illustrate star and bus networks as well as hybrids involving both these networks.

Hardware should include communications links (cables, microwave, fibre optics and so on) hub, switch, node and router.

Students must know that standard protocols are a set of rules that are internationally recognized in the transmission of data. The difference between data security and data integrity must also be recognized. Students do not need to know specific or technical details such as the ISO (OSI) system of layers, TCP/IP and so on.

Students must understand the role of communications software in connecting local and wide area networks and the need to deal with protocols and data security.

Error-checking codes such as check sums (block character checks) and parity checks must be understood. The reasons for re-transmission should be understood. The quality of communication lines should be considered.

Students should understand the concept of data encryption but do not need to give algorithmic details. They must understand the need for, and use of, passwords, physical security and different levels of access (permissions) for different users.

Students must know that documents and graphics files can be sent in different formats and the format affects the speed of transmission. Common formats such as JPEG and BMP should be known. The principles of data compression should be considered but details of methods are not required.

The use of LANs, public and private WANs and the Internet should be considered.

Specific names of browsers and search engines are not required.

Students must understand the relationship between number of digits and number of patterns available (2n),for example: 4-bit colour representation allows 16 colours; a 32-bit address bus can address 4GB RAM). The different features of ASCII and Unicode should be known but students are not expected to know the specific representations of characters.

Link with 3.4.8 and 3.4.9.

Students need to understand the need for conversion between data for processing, for example, sensors and modems.

Teachers are free to choose the second application. Other software examples include: speech recognition, light detection, image processing, OCR software.

Verification and validation should be understood. Check digits and hash totals should be explained. The use of modulo operators (mod, div) in constructing check digits should be understood.

Re-input, re-transmission and restoring from backups should be considered. Error-correcting algorithms are not required.

The required file manager functions are: copy, delete, format, find, create folder/directory, archive, print, back-up, rename and restore. The fact that files are not stored contiguously only needs to be dealt with in outline, in order to understand why defragmentation software is required. Technical details are not required.

For binary and hexadecimal calculations, only addition is required.

For negative binary numbers in integer and real formats, only the method-of-two’s complement is required.

Both fixed-point and floating-point representations are required. Students should be able to calculate the range of normalized floating-point numbers given a specific representation. Issues such as the need for normalization and the loss of precision should be understood.

This can be written in words as: (A xor not B) and (C nor D).

A maximum of three inputs will be expected. Include the use of truth tables to determine whether two Boolean expressions are logically equivalent.

A maximum of three inputs will be expected. Conversions may be done “algebraically” (using identities such asand De Morgan’s laws) or by using Karnaugh maps, Venn diagrams or any other appropriate method.

Students will be given a hash algorithm and a set of keys or records that will be allocated memory locations by employing the algorithm.

This includes: to initialize a stack, to test for an empty or a full stack, to push a data item, to pop a data item and to display the top data item. All operations must protect against overflow and underflow.

This includes: to initialize a queue, to test for an empty or a full queue, to add a data item to the rear of a queue (enqueue), to remove a data item from the front of a queue (dequeue) and to display the data item at the front of a queue. Algorithms must include linear and circular implementation. All operations must protect against overflow and underflow.

This includes: initialize, add objects, delete objects, find tail object, perform linear search and insert objects into a list. All operations must protect against null pointer exceptions

Students must recognize the difference between this and the static representation of stacks. See notes in 5.2.5

Students must recognize the difference between this and the static representation of a queue. See also notes in 5.2.7.

This includes: initialize, add objects, traverse (pre-order, in-order and post-order). All tree traversals must be implemented recursively. See 5.5.

This should be limited to the following definition.

An object is a combination of data and the operations that can be performed in association with that data. Each data part of an object is referred to as a data member while the operations can be referred to as methods. The current state of an object is stored in its data members and that state should only be changed or accessed through the methods. Common categories of operations include: the construction of objects; operations that either set (mutator methods) or return (accessor methods) the data members; operations unique to the data type; and operations used internally by the object.

Encapsulation is the combination of data and the operations that act on the data into a single “program unit” called an object. The advantages are that it allows for information and data hiding.

Once encapsulated into an object both the data members and the details of the implementation of the member functions can be hidden. This allows the object to be used at an abstract level.

Polymorphism describes the situation in which the same operation can be applied to different objects, with each object behaving appropriately. The concepts of templates, virtual member functions and operator overloading are not required. Polymorphism allows objects to be used intuitively and it simplifies coding by making it generic.

Inheritance allows one object to be derived from another. The derived object has all the data members and member functions of the original object and any additional data member or member functions that are defined within it. Even previously defined functionality may be redefined with the appropriate functionality applied to the particular object that invokes it. In Java, all classes are subclasses of the object class. When functions (including constructors) are redefined in a derived object, they completely override the original function. Inheritance in Java is limited to one object being derived from another (one level of inheritance). Multiple inheritance is not supported by the Java language.

This will include recording the behaviour and state of the objects.

Students must understand that for some applications a recursive procedure is short and elegant, and that a recursive solution is ideally suited for some algorithms. However, recursion is not suitable for most algorithms as non-recursive ones are more efficient.

All steps and calls must be shown clearly. Students may need to draw a tree.

This is limited to an algorithm that returns no more than one result and contains either one or two recursive calls to itself.

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When students are presented with an algorithm that they have not encountered they must be able to write the BigO notation for the efficiency of that algorithm

Students should consider the needs of different applications for data types and data structures. For example, stacks might be used to track changes to a word processing document whereas a queue might store data items being entered at the keyboard for subsequent processing in the order in which they arrived. Ordered binary trees and hash tables are frequently used to store key fields used for quick retrieval of items from an unordered data file.

The algorithms may be  standard algorithms mentioned in the syllabus, or algorithms of equivalent complexity that the students have not seen before.

Further details (or registers) are not required.

Knowledge of any specific operating system is not required.

Students need to be aware that an operating system is a collection of programs that cover the following tasks: input/output (I/O) control, file maintenance, software/hardware interface, memory management, user interface, software execution control, security. Virtual memory must be included but knowledge of thrashing and paging is not required. This extends 3.3.2.

The roles of providers, servers and clients should be understood for each of these networks. Students should be able to select the appropriate type of network for a given situation. They must understand the role of gateways.

Ethernet, public and private telephone lines, ISDN, ADSL, fibre optic and wireless methods should all be familiar and students should be able to select the most suitable method of communication in a given situation, and to state the advantages of each method. Technical details will not be required.

Students need to be aware that when a message is dissembled into packets, the packets may take different paths and pass through different nodes to arrive at the same destination, and that packets can be discarded. Virtual circuits are not required.

Students do not need to know technical details of TCP, IP, OSI, but must understand that protocols include essential information that allows packets to be reassembled at their destination according to the requirements of the receiving computer.

Emphasize the importance of protection within a LAN by giving layered access (for example, via permissions on certain areas) to different users, and marking files as read only. The need for a firewall to prevent intrusion from outside should be clear.

This must include the use of buffers (including double buffering), interrupts and interrupt priorities, polling, direct memory access (DMA) and handshaking in these devices.

Students must cover an event or external device interrupt as well as a polling system. Knowledge of specific interrupt codes is not required.

A partially-indexed sequential file has ordered records, with a separate but partial index. Students should be able to describe how records can be retrieved via access to the index, followed by direct access to the first record in a group, followed by sequential access to locate the desired record.

A fully-indexed file has unordered records, with a separate and complete index. Students should be able to describe how records can be retrieved via access to the index, followed by direct access in the data file. Recall of multi level indexes is not required.

A direct access file can have unordered records. Students should be able to outline how records can be retrieved via a calculation followed by direct access.

Students should understand the use of modulo operators (mod, div) in the construction of a hash function. See also 5.2.3.

This should also include storage media (disk, tape). Access speeds should be expressed in descriptions, calculations of iterations and BigO notation.

For example, in a fully-indexed sequential file, records can be retrieved in alphabetical order by using the index, even though they are not stored physically in that order.

The sorting of files that are too large for the primary memory of a computer requires techniques based on a combination of sorting and merging. Recall of algorithms for merge sorts is not required.