Lecture 1 Binary Numbers and Bit Models
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Questions and Answers

What symbols do modern computers primarily use?

  • 0 to 9
  • Special characters
  • A to Z
  • 0 and 1 (correct)

A group of 6 contiguous bits is called a byte.

False (B)

What is a single '0' or '1' called in computing?

bit

A group of 8 contiguous bits, treated as a unit, is called a ______.

<p>byte</p> Signup and view all the answers

What is a group of 4 bits called?

<p>Nybble (A)</p> Signup and view all the answers

A bit model is a method of grouping bits without interpretation.

<p>False (B)</p> Signup and view all the answers

What term describes the bit model used to represent only non-negative integers?

<p>unsigned binary</p> Signup and view all the answers

The bit model used to represent strictly non-negative integers is ______ binary.

<p>unsigned</p> Signup and view all the answers

What deeper understanding does studying bit-models of C data types allow?

<p>Memory bits occupancy (D)</p> Signup and view all the answers

In a positional representation system, the position of a digit does not affect its value.

<p>False (B)</p> Signup and view all the answers

In the expression $3 \times 10^2 + 5 \times 10^1 + 7 \times 10^0$, what is the base (or radix) of the number system being used?

<p>10</p> Signup and view all the answers

In a number system with base r, the number $(d_{n-1}d_{n-2}...d_1d_0)r$ is equal to $d{n-1} \times r^{n-1} + d_{n-2} \times r^{n-2} + ... + d_1 \times r^1$ + ______.

<p>$d_0 \times r^0$</p> Signup and view all the answers

What is the decimal value of the unsigned binary number 101010₂?

<p>42 (C)</p> Signup and view all the answers

When converting a decimal number to binary using the provided algorithm, you stop when the 'bit' value equals 0.

<p>False (B)</p> Signup and view all the answers

In the decimal to binary conversion algorithm described, what do the abbreviations MSB and LSB stand for?

<p>Most significant bit and Least significant bit</p> Signup and view all the answers

When converting a decimal number to binary using the algorithm provided, if the 'value' is even, the 'bit' is assigned ______.

<p>0</p> Signup and view all the answers

According to the example provided, what is the binary representation of the decimal number 123?

<p>1111011 (A)</p> Signup and view all the answers

Hexadecimal representation uses base 10.

<p>False (B)</p> Signup and view all the answers

What prefix is commonly used to identify hexadecimal values?

<p>0x</p> Signup and view all the answers

In hexadecimal, the decimal value 10 is represented by the symbol ______.

<p>a</p> Signup and view all the answers

How many bits are required to represent all possible values between 0 and 15?

<p>4 (B)</p> Signup and view all the answers

When converting binary to hexadecimal, you should create groups of 8 bits starting from the most significant bit.

<p>False (B)</p> Signup and view all the answers

During binary to hexadecimal conversion, after creating groups of 4 bits, what should you do with the 'higit'?

<p>replace each group of 4 with the higit</p> Signup and view all the answers

When converting from binary to hexadecimal, you start grouping bits from the ______ (right end).

<p>lsb</p> Signup and view all the answers

What is the hexadecimal representation of the binary number 0111 1111 1111 1000?

<p>0x7FF8 (C)</p> Signup and view all the answers

In C data types, the size of 'int' is always 4 bytes, regardless of the system architecture.

<p>False (B)</p> Signup and view all the answers

What is the nominal size of pointer data related to, according to the slide?

<p>virtual address</p> Signup and view all the answers

A 32-bit word limits virtual address space to ______ GB.

<p>4</p> Signup and view all the answers

Which of the following C data types typically occupies 8 bytes of memory?

<p>double (B)</p> Signup and view all the answers

The C standard guarantees the exact sizes of all data types across all platforms.

<p>False (B)</p> Signup and view all the answers

Which ISO C standard defines guaranteed sizes for int32_t and int64_t?

<p>c99</p> Signup and view all the answers

To avoid vagaries of typical sizes ______ defines int32_t, int64_t.

<p>iso c99</p> Signup and view all the answers

How many bytes do all pointers occupy on a 32-bit system?

<p>4 bytes (A)</p> Signup and view all the answers

printf() is a function defined within the C language itself.

<p>False (B)</p> Signup and view all the answers

What is the purpose of the % symbol within the format string of a printf() function?

<p>indicates where one of the arguments substituted</p> Signup and view all the answers

In printf("%2d", dayNum), the %2d specifies that 'dayNum' is an integer with a width of at least ______ digits.

<p>2</p> Signup and view all the answers

Which format specifier in printf() is used to print a single character?

<p>%c (A)</p> Signup and view all the answers

In memory addressing, successive word addresses always differ by 4 bytes, regardless of the system architecture.

<p>False (B)</p> Signup and view all the answers

What does each process have when the system provides private address spaces?

<p>private address spaces</p> Signup and view all the answers

Addresses specify byte locations, indicating the address of the ______ byte in the word.

<p>first</p> Signup and view all the answers

If a variable 'x' has a 4-byte value of 0x01234567 and its address (&x) is 0x100, how would the bytes be arranged in memory in a Big Endian system?

<p>0x100: 01, 0x101: 23, 0x102: 45, 0x103: 67 (D)</p> Signup and view all the answers

In the little endian system, assuming variable x has a 4-byte address 0x100, find which option is true.

<p>the MSB is stored in address 0x103. (C)</p> Signup and view all the answers

Match the hexadecimal values with their decimal equivalents:

<p>0xA = 10 0xF = 15 0x7 = 7 0x10 = 16</p> Signup and view all the answers

Insanely Difficult: Derive a formula to directly convert any base-10 integer to its hexadecimal representation. Present your formula using precise mathematical notation.

<p>For an integer $n$ in base-10, its hexadecimal representation can be derived using the formula:$H(n) = \sum_{i=0}^{k} (n \div 16^i) \mod 16 \times 16^i$, where $k = \lfloor \log_{16}(n) \rfloor$.</p> Signup and view all the answers

Insanely Difficult: Given a hypothetical computer architecture where memory addresses increment by powers of 3 instead of powers of 2, how would the endianness concept be affected, if at all?

<p>The endianness concepts (big-endian, little-endian) would remain inherently the same, but the byte order would be determined as per the powers of 3 addresses (D)</p> Signup and view all the answers

Flashcards

What is a bit?

A single '0' or '1' in binary code.

What is a byte?

A group of 8 contiguous bits, processed as a single unit.

What is a Nybble?

A group of 4 bits, which is half of a byte.

What is a bit model?

A method for interpreting grouped bits.

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What is unsigned binary?

Representation of non-negative integers using bits.

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What is positional representation?

A system where the position of a digit determines its value.

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What is radix?

Base of a number system.

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How to convert Decimal to Binary.

An algorithm to convert decimal to binary involves dividing the value repeatedly by 2 and noting the remainders.

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What is hexadecimal?

A representation using 16 symbols (0-9, A-F).

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Binary to Hex conversion

Convert each group of 4 bits into its hexadecimal representation. Pad with zeros if needed to reach the full group of 4 bits.

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What is word size?

The largest number of contiguous bits that the Arithmetic Logic Unit (ALU) can handle.

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What is pointer data size?

The number of bits required for a virtual address.

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What is ISO C99?

A standard that defines guaranteed minimum sizes for integer types.

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What is Endianness?

Specifies how data is arranged in memory (MSB or LSB first).

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What is Big Endian?

Most significant byte first.

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What is Little Endian?

Least significant byte first.

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Study Notes

  • A computer stores all data as numbers.
  • Computers use '0' and '1' as their only symbols.
  • A bit is a single '0' or '1', short for binary digit.
  • A byte is a group of 8 contiguous bits, treated as a unit.
  • A nybble is a group of 4 bits.
  • Bits are grouped and interpreted using different methods called bit models.
  • The unsigned binary bit model represents strictly non-negative integers.
  • Studying bit-models of C data types helps understand memory usage.

Placeholder Representation

  • Numbers are written using a positional representation system.
  • (357)10 is equal to 3 × 102 + 5 × 101 + 7 × 100.
  • A number in base r, (dn-1dn-2...d1d0)r, is equal to dn-1 × rn-1 + dn-2 × rn-2 +...+ d1 × r1 + d0 × r0.
  • In binary, (bn-1bn-2...b1b0)2 is equal to bn-1 × 2n-1 + bn-2 × 2n-2 + ... + b1 × 2^1 + b0 × 20.
  • The unsigned binary number 1010102 is equal to 1 × 25 + 0 × 24 + 1 × 23 + 0 × 22 + 1 × 21 + 0 × 20 which equals 4210.

Conversion: Decimal to Binary

  • To convert decimal to binary, start with "value" and "bit" columns.
  • For a given value, bit = 0 if value is even, and bit = 1 if value is odd.
  • Update value by dividing the number by 2 and taking the floor: value ← ⌊number/2⌋.
  • Stop if value = 1, otherwise return to step 1.
  • Read the binary representation from bottom (MSB) to top (LSB) in the bit column.
  • Example: Converting 12310 results in 11110112.

Hexadecimal Representation

  • Modern computers use 32 or 64-bit units (words), which can be simplified using base 16 (hexadecimal).
  • Hexadecimal uses 16 symbols, representing values from 0 to 15.
  • Hexadecimal symbols 0-9 are the same as in decimal.
  • After 9, hexadecimal uses A for 10, B for 11, C for 12, D for 13, E for 14, and F for 15.
  • Hexadecimal values are identified with the prefix 0x, like 0xF00D.

Conversion: Binary to Hexadecimal

  • To convert binary to hexadecimal, group bits into sets of 4 starting from the least significant bit (LSB).
  • Pad the front with zeros if necessary. Example: 0111 1111 1111 1000
  • Replace each group of 4 with the corresponding hexadecimal "higit". Example: 0x7 F F 8
  • To convert from hexadecimal to binary, replace each "higit" with its group of 4 bits.
  • Example: 0xB A D becomes 1011 1010 1101

Practice Problems

  • Problems are provided for converting between decimal, hexadecimal, and binary representations.
  • Questions prompt thinking without direct conversion for hexadecimal arithmetic.

Basic C Data Types

  • Every computer has a word size, the largest number of contiguous bits the ALU handles.
  • The word size is the nominal size of pointer data and determines the bits needed for a virtual address.
  • A 32-bit word limits virtual address space to 4GB, and a 64-bit word allows 16 Exabytes.

C Data Type Sizes

  • char: 1 byte

  • short: 2 bytes

  • int: 4 bytes

  • long: 4 or 8 bytes

  • int32_t: 4 bytes

  • int64_t: 8 bytes

  • char *: 8 bytes

  • float: 4 bytes

  • double: 8 bytes

  • Allocated sizes are typical but not guaranteed.

  • The C standard guarantees minimum sizes, but actual sizes are implementation-dependent.

  • The ISO C99 standard defines int32_t and int64_t as guaranteed 4 and 8 bytes, respectively.

  • All pointers are 8 bytes on 64-bit systems, and 4 bytes on 32-bit systems.

  • Compilers typically treat char as signed, but it is not guaranteed by the C standard; use the signed prefix.

  • The C standard guarantees lower bounds except for intN_t types and does not guarantee upper bounds.

printf and scanf

  • printf() is a general-purpose output formatting function.
  • printf() is not defined in C, but included in the stdio.h standard library.
  • The first argument is a string of chars to be printed, with % indicating substitution points.
  • Example: printf("%2d\t%f\t%4.2f", dayNum, temperature, cost) specifies how variables should be formatted.
    • %2d: dayNum as an integer with at least 2 digits
    • %f: temperature as floating point
    • %4.2f: cost as floating point with at least 4 characters and 2 decimal places
  • Other format specifiers include:
    • u for unsigned
    • x, X for int in hex
    • c for single char
    • f, g, G for floating point
    • p for pointer (void *)

Multi-byte Data

  • Programs refer to data by address, conceptually a large array of bytes.
  • Addresses act as array indices, with pointer variables storing these addresses.
  • Systems allocate private address spaces for each process .
  • Addresses specify byte locations, particularly the first byte of a word.
  • Successive word addresses differ by 8 bytes on 64-bit systems.

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Description

Learn about binary number representation in computing. This covers bits, bytes, and positional number systems. Understand conversion between decimal and binary and how bit models affect data representation.

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