Representation of Information and Computers

For binary 11010, adding the weights of the digits that are 1 — 16, 8, and 2 — gives 16 + 8 + 2 = 26. 22 and 24 come from miscounting the digit weights, and 28 is the value obtained by wrongly adding a 0 digit (the 4s place), as in 16 + 8 + 4; all are wrong.

Dividing 200 by 16 gives quotient 12 (= C) with remainder 8, so in hexadecimal it is C8. BC is decimal 188, D8 is 216, and E8 is 232 — none of them is 200. Remember that a single hexadecimal digit is written 0-9 and A (10) through F (15).

Binary and hexadecimal correspond 4 bits to 1 digit. Splitting 10111100 into groups of 4 bits gives 1011 = B and 1100 = C, so the answer is BC. CB swaps the upper and lower halves, B4 misreads the lower 4 bits as 0100, and DC misreads the upper bits as 1101.

Inverting every bit of 5 = 00000101 gives 11111010, and adding 1 gives 11111011, the two's complement representation of -5. 11111010 is only the inverted bits (the one's complement), 10000101 is a wrong representation that merely sets the sign bit, and 00000101 is +5.

The prefixes grow in the order K (kilo) → M (mega) → G (giga) → T (tera) → P (peta) → E (exa): each step is 1,000 times larger in decimal, or 1,024 times in binary. The other options swap M and G, or G and T, and are wrong.

Each of the 8 bits can be 0 or 1, so the total is 2 to the 8th power = 256 patterns. 255 is the maximum unsigned integer value (the largest of 0-255), not the total count. 128 is 2 to the 7th and 512 is 2 to the 9th, which come from miscounting the bits.

The place values of binary fractions are 0.5, 0.25, 0.125, and so on. Since 0.625 = 0.5 + 0.125, setting 1 in the 0.5 and 0.125 places gives 0.101. 0.110 is 0.75, 0.011 is 0.375, and 0.100 is 0.5 — none of them is 0.625.

Since 1 byte is 8 bits, 1,024 bytes × 8 = 8,192 bits. 1,024 leaves the value in bytes, and 2,048 and 4,096 merely multiply by 2 and 4; forgetting the basic conversion of 1 byte = 8 bits leads to these errors.

Floating-point representation expresses a real number as a pair of mantissa and exponent, handling a very wide range of values within a limited bit length. It is not integer-only, nor a string conversion mechanism. Values that cannot be expressed exactly in binary incur rounding error, so the claim of error-free representation is also wrong.

UTF-8 is one of the encoding schemes for Unicode, which covers many languages; it represents 1 character in a variable length of 1 to 4 bytes. Characters in the ASCII range are represented unchanged in 1 byte, giving high compatibility. It is neither Japanese-only nor fixed-length, and a 7-bit code describes ASCII.

ASCII is the basic character code representing alphanumerics, symbols, and control characters in 7 bits. It cannot represent kanji; kanji are handled by multibyte codes such as JIS kanji and Shift-JIS. Unicode encoding schemes include UTF-8, and image compression formats include JPEG; neither describes ASCII.

Shift-JIS is a representative multibyte code for Japanese, mixing 1-byte alphanumerics with 2-byte kanji and kana. A 7-bit code describes ASCII, and audio encoding describes PCM and the like. The fixed 4-byte claim is also wrong: Shift-JIS is variable-length, 1 or 2 bytes.

JSON is a lightweight text format that represents data structures using name-value pairs and arrays, and is widely used for data exchange between systems. Comma-separated tabular text is CSV, tag-based structure markup is XML or HTML, and a print-preserving document format describes PDF.

JPEG is a lossy-compression image format that achieves high compression ratios by discarding information the human eye barely notices. PNG and GIF use lossless compression, which can fully restore the original data, and BMP is basically an uncompressed format. Note also that with lossy compression, image quality can degrade each time it is compressed.

H.264 is a video compression and encoding standard, widely used as part of the MPEG family, with HEVC (H.265) as its successor. JPEG and PNG are still image formats and WAV is an audio data format; none is a video compression standard.

Logical AND is 1 only when both inputs are 1, so with A = 1 and B = 0 it is 0. OR is 1 if either input is 1, and XOR is 1 when the inputs differ, so both give 1. NAND is the negation of AND, so negating AND = 0 gives 1. It helps to confirm with a truth table.

The sampling theorem states that the original signal can be reproduced by sampling at a frequency at least 2 times the highest frequency contained in the signal. Half the frequency, or the same frequency, cannot reproduce the waveform. The number of quantization bits determines the fineness of values (number of levels), a separate factor from the sampling frequency.

In A/D conversion, sampling first takes the signal's values at fixed intervals, quantization then rounds the sampled values into a finite number of levels, and encoding finally turns them into binary codes. Sampling → quantization → encoding is the correct order; the other options rearrange it.

24-bit color is 3 bytes per pixel, so 800 × 600 × 3 = 1,440,000 bytes, about 1.44 MB. About 0.48 MB is the value computed at 1 byte per pixel, and about 2.88 MB and 5.76 MB are 2 times and 4 times too large — errors that easily arise from mixing up bits and bytes.

Of the 5 classic units, the CPU combines the control unit, which decodes instructions and directs the other units, and the arithmetic unit, which performs computations. Input and output units move data in and out, and main memory and auxiliary storage store data; they are not components of the CPU.

RAID1, called mirroring, writes the same data to 2 disks, so no data is lost if 1 disk fails. RAID0 is striping, aiming only at speed with no redundancy. RAID5 distributes parity across the disks, and RAID6 keeps parity twice over.

RJ-45 is the LAN connector used on UTP cables for wired LAN (Ethernet). USB uses its own family of USB connectors, HDMI uses the HDMI port for video and audio, and RS-232C uses serial connectors such as the 9-pin D-sub; none of them is RJ-45.

Batch processing collects data over a period and processes it in bulk, for example overnight, and suits jobs like monthly aggregation. Real-time processing responds to requests immediately, distributed processing splits work across multiple computers, and online processing is processing performed over a network connection.

Software is classified into the OS, which manages the hardware; middleware, which sits between the OS and applications providing common functions; and application software used directly for work. Spreadsheets are applications, the OS is basic software, and a DBMS is middleware; the other options mix up the categories.

Providing entry screens for clinical records is a function of application software such as the electronic medical record. OS functions include memory management, task and process management, hierarchical file system management, peripheral device control, network support, and user management; the OS does not perform the business processing itself.

A DBMS is middleware that sits between the OS and applications and provides data management functions. Transaction processing monitors and operations management tools are also middleware. Web browsers and spreadsheets are application software, and Linux is an OS, so their classifications differ.

Spreadsheet software is application software used directly in the user's work. A device driver is software that controls peripheral devices, a transaction processing monitor (TP monitor) is middleware, and an operating system is basic software; none of them is classified as an application.

A stack is a last-in, first-out (LIFO) data structure in which data is added and removed at one end only. A queue is first-in, first-out (FIFO) and is used for waiting lines. A linear list links elements with pointers, and a binary search tree is a tree structure that places elements according to their order relation.

Bubble sort is a basic sorting algorithm that repeatedly compares adjacent elements and swaps them when needed. Quicksort is a fast sorting method that repeatedly partitions data into groups larger and smaller than a pivot — a different approach. A binary search tree and a linear list are data structures, not sorting algorithms.

JavaScript is the representative language that runs in the Web browser and adds interactivity to Web pages. Despite the similar name it is a different language from Java, which is mainly used for server-side and business system development. C is used for developing OSes and embedded software, and SQL is a language for operating databases.