4.1 Data Types (OCR A Level Computer Science) Flashcards

True.

Unicode supports a wide range of characters including emojis, while ASCII is limited to 128 basic characters.

A data type is a classification that specifies which type of data a variable can hold, such as integer, real, char, string, or boolean.

A integer is used to represent whole numbers, while a real represents numbers with fractional parts.

Casting is the process of converting one data type to another in a program, such as turning a string into an integer.

Sign and magnitude is a method for representing positive and negative binary numbers where the most significant bit indicates the sign and the remaining bits represent the magnitude.

The number is positive if the MSB is 0, and negative if the MSB is 1.

A bit is the smallest unit of digital information, representing either an "off" (0) or an "on" (1) state.

In an 8-bit binary number, the leftmost digit represents the value 128, which is 2 to the power of 7.

A byte is made up of 8 bits, and groups of bits allow us to represent more complex information.

True.

Encoding schemes like ASCII for text or JPEG for images allow binary values to be interpreted as different types of information.

Denary numbers are the base-10 number system, used by humans, and consist of digits 0 to 9.

Binary numbers are the base-2 number system, using only the digits 0 and 1, commonly used by computers to store data.

Computers use binary numbers to store data because their circuits and switches have two states: on (1) and off (0).

The 8-bit binary number 01101001 can be converted into denary using place values. Its denary value is 105.

The denary number system is a base-10 number system that uses digits from 0 to 9.

The binary representation of the denary number 101 is 01100101.

To convert a denary number to binary, we start by writing out the binary number system values: 128, 64, 32, 16, 8, 4, 2, 1.

False.

A 1 is placed in the binary column only if the column value is less than or equal to the current remainder when converting from denary to binary.

A signed binary number is a binary number that can represent both positive and negative values.

The Most Significant Bit (MSB) in signed binary numbers indicates whether the number is positive (MSB is 0) or negative (MSB is 1).

Unsigned binary numbers are used to represent positive, while signed binary numbers can represent both positive and negative values.

True.

In both sign & magnitude and two's complement, the Most Significant Bit (MSB) represents the sign: 0 for positive and 1 for negative.

A sign and magnitude binary number is a binary number where the most significant bit (MSB) represents the sign (0 for positive, 1 for negative) and the remaining bits represent the magnitude.

To convert a sign and magnitude binary number to denary, convert the magnitude as normal, then apply the sign at the end.

True.

The MSB is used for the sign instead of value, so the maximum positive value is halved compared to unsigned binary.

Two's complement is a method for representing negative binary numbers by inverting the bits of the positive number and adding one.

In two's complement, the MSB represents the negative starting point of the number, and the remaining bits count upwards from that value.

To convert a positive binary number to its two's complement negative equivalent, you must invert the bits and add one.

True.

Two's complement allows for simpler arithmetic operations, making calculations less computationally intensive compared to sign and magnitude.

Binary addition is the process of summing numbers in base-2, using only the digits 0 and 1, moving from right to left and carrying over when the sum in a column is greater than 1.

If the sum of a binary column is greater than 1, the excess is carried over to the next left column.

In binary addition, if the sum of a column is more than 1, you must carry over the extra to the next column on the left.

True.

In signed number representations, overflow can flip the sign bit, incorrectly changing the sign of the result.

The two's complement is a method used to represent negative binary numbers and to perform binary subtraction by adding the two's complement of the number to be subtracted.

The main advantage of using two's complement for binary subtraction is that subtraction can be performed as an addition operation, which simplifies the design of digital circuits.

To subtract a binary number using two's complement, first invert all the bits of the number to subtract, then add 1 to it.

False.

When using two's complement to subtract binary numbers, the overflow bit is ignored and not included in the final answer.

A hexadecimal number is a base-16 system that uses the digits 0-9 and the letters A-F.

Hexadecimal is more concise and easier for humans to read and write, since each hexadecimal digit represents four binary bits.

False.

Hexadecimal uses the digits 0-9 and the letters A-F, not G-L.

Hexadecimal values are commonly used to define colours because they can represent very large binary numbers more concisely.

A hexadecimal lookup table is a reference chart used to quickly convert between denary, binary and hexadecimal values.

In hexadecimal, the denary number 10 is represented as A.

False.

In hexadecimal, after 9 the next digit is A, not 10.

A subscript in number representation indicates the base of a number, helping to differentiate between number systems such as binary, denary, and hexadecimal.

The hexadecimal equivalent of the denary number 241 is F1.

To convert a denary number to hexadecimal, first convert it to binary, then split it into nibbles of 4 bits.

A nibble is a group of 4 bits in binary, often used when converting binary to hexadecimal.

True.

In hexadecimal, F corresponds to the denary value 15.

The hexadecimal equivalent of 11010101 is D5.

To convert a binary number to hexadecimal, split the binary into nibbles of four bits each.

A nibble is a group of four bits in binary, often used to represent a single hexadecimal digit.

True.

Each hexadecimal digit can be directly mapped to a nibble (four binary digits).

The binary equivalent of the hexadecimal number B2 is 10110010.

To convert a hexadecimal number to binary, split it into two digits and convert each to a nibble.

A nibble is a group of 4 bits in binary, often used to represent a single hexadecimal digit.

True.

Each hexadecimal digit is converted to a 4-bit nibble, and the two nibbles are joined to make a byte.

Floating point binary is a method of representing real numbers in binary form, allowing for both fractional and whole-number components, and enabling efficient representation of very large or very small values by adjusting the floating point.

The two main components of a floating point number are the mantissa, which holds the actual digits and represents precision, and the exponent, which determines the scale by moving the binary point left or right.

In floating point binary, the mantissa holds the significant digits, while the exponent determines the scaling factor.

True.

Negative floating point numbers use two's complement for representation, with the MSB indicating the sign and the remaining bits representing the value.

A floating point binary number is a way of representing real numbers in binary, using a mantissa and an exponent.

The first step is to represent the number in fixed point binary.

True.

The exponent tells you how many places and in which direction the decimal point has been moved in the mantissa.

When converting 6.75 to floating point binary, the mantissa is 011011 and the exponent is 011.

The mantissa is the part of a binary floating point number that represents the significant digits of the number.

The exponent in a binary floating point number shows how many places to move the binary point to get the denary value.

To convert a binary floating point number to denary, first write out the binary digits, then move the binary point as many places to the right.

True.

Moving the binary point three places to the right in 0.1100 gives 110.0, which is 6 in denary.

A normalised floating point binary is a floating point number where the mantissa starts with either 01 or 10, ensuring a consistent format for representation and making arithmetic and comparisons straightforward.

A floating point number is normalised when the mantissa starts with 01 or 10.

Normalising floating point binary numbers ensures a consistent format for representation, making arithmetic operations and comparisons more straightforward.

True.

When normalising, shifting the decimal point to the left increases the exponent value, while shifting it to the right decreases the exponent.

The mantissa is the part of a floating point number that contains its significant digits.

Normalisation in floating point numbers means adjusting the mantissa and exponent so that the mantissa is within the allowed range (e.g., between 1.0 and 1.111... in binary).

A floating point number is represented using a sign, mantissa, and exponent.

Before adding or subtracting floating point numbers, you must make sure both numbers have the same exponent.

A floating point number consists of a sign, mantissa, and exponent.

False.

The sign of the result depends on the signs and magnitudes of the numbers being added.

To normalise a floating point result, shift the mantissa and adjust the exponent.

You must align the exponents by shifting the mantissa of one number and adjusting its exponent so both numbers have the same exponent.

A logical binary shift is an operation where all the bits in a binary number are moved left or right by a specified number of positions, commonly used in computer programming and digital systems.

Each time a binary number is shifted one place to the left using a logical shift, its value is doubled.

True.

A logical right shift moves all bits to the right, and for each position shifted, the value of the binary number is halved.

There are two types of logical binary shifts: Left and Right.

A mask is a binary number used in bitwise operations to isolate, modify, or test specific bits in another binary value.

A mask is used to isolate specific bits in a binary number, such as extracting, setting, clearing, or toggling them.

The bitwise AND operation compares each bit of the binary number with the mask, and the result is 1 only if both bits are 1. This operation is commonly used to extract specific bits from a binary number.

False.

The bitwise OR operation sets a bit to 1 if either the binary number or the mask has a 1 in that position.

A character set is a list of all characters and their associated binary codes. Character sets standardise the binary representation of each character for computers.

ASCII is the American Standard Code for Information Interchange, a character set that uses 7 bits to encode 128 distinct characters.

Computers need character sets to standardise the binary codes for each character, ensuring compatibility between different hardware and software.

Each character in standard ASCII is encoded using 7 bits, allowing for 128 distinct characters.

False.

ASCII is limited to 128 characters and cannot represent characters from languages other than English.

The binary code 01000001 represents the character A in ASCII.

ASCII is an encoding system that uses 7 bits to represent 128 characters, mainly for the English language.

Unicode is a universal character encoding system that uses up to 32 bits to represent characters from many languages and scripts worldwide.

True.

Unicode supports a much larger range of characters than ASCII, including characters from different scripts and emoji.

ASCII uses 7 bits to represent characters, while Unicode can use up to 32 bits.