Computer Fundamentals - 3

In coincident-current core memory, each core is threaded by 4 wires: 2 X wires (row selection), 2 Y wires (column selection), plus sense and inhibit lines that can be shared. The total unique wires passing through cores is 8 when counting all signal paths.

A MODEM (MOdulator-DEModulator) works by modulating a digital signal onto an analog carrier wave for transmission, then demodulating it back at the receiver. The digital signal modifies characteristics like amplitude, frequency, or phase of the carrier.

Baud rate measures signal changes per second, while bit rate measures data bits per second. The relationship varies: they can be equal (1 bit per signal), baud can be higher (multi-level signaling with <1 bit per change), or bit rate can be higher (multiple bits per baud with compression/encoding). Thus, no fixed relationship always holds.

Hard disks provide the fastest information retrieval among the options because they use spinning platters with movable read/write heads that can rapidly access any sector. Floppy disks are slower due to lower rotational speeds and mechanical limitations, while magnetic tape is sequential access only, making it the slowest for random retrieval.

To convert 71 from decimal to binary, we find powers of 2: 71 = 64 + 4 + 2 + 1 = 2^6 + 2^2 + 2^1 + 2^0. Reading from 2^6 down to 2^0, we write 1 for each power present and 0 for absent powers, giving 1000111.

A fully connected mesh topology provides the highest reliability because every node has a direct connection to every other node. If any single link fails, communication can still occur through alternative paths. Star topology fails if the central hub fails, bus topology fails if the backbone is cut, and ring topology fails if any link breaks.

Ring topology is not broadcast because data flows sequentially from one node to the next in a unidirectional manner. Each node receives and forwards the signal to its single downstream neighbor. In contrast, star and tree broadcast from the central node, and bus broadcasts on the shared medium to all connected nodes simultaneously.

To convert 99 from decimal to binary: 99 = 64 + 32 + 2 + 1 = 2^6 + 2^5 + 2^1 + 2^0. Writing bits from 2^6 to 2^0 (positions 6,5,4,3,2,1,0), we have 1s at positions 6,5,1,0 and 0s at positions 4,3,2, giving 1100011.

To convert 28 from decimal to octal: divide by 8 repeatedly. 28 ÷ 8 = 3 remainder 4. Then 3 ÷ 8 = 0 remainder 3. Reading remainders from bottom to top gives 34. Verification: 3×8^1 + 4×8^0 = 24 + 4 = 28.

Bubble memory technology uses thin films of garnet (typically garnet ferrite) as the magnetic material. These garnet films have magnetic domains that can form stable 'bubbles' representing data bits. Magnetic cores are used in core memory, cobalt has some applications but garnet is the standard for bubble memories, and metallic materials are not suitable for bubble formation.

To convert 67 from decimal to octal: divide by 8 repeatedly. 67 ÷ 8 = 8 remainder 3. Then 8 ÷ 8 = 1 remainder 0. Finally 1 ÷ 8 = 0 remainder 1. Reading remainders from bottom to top gives 103. Verification: 1×8^2 + 0×8^1 + 3×8^0 = 64 + 0 + 3 = 67.

Binary to decimal conversion uses powers of 2 from right to left (2^0, 2^1, 2^2, etc.). Starting from the right: 1(1) + 1(2) + 0(4) + 1(8) + 1(16) + 0(32) + 1(64) = 91.

Convert each hex digit to its 4-bit binary equivalent: 6→0110, B→1011, 2→0010. Concatenate: 011010110010, which simplifies to 11010110010.

Each octal digit converts to 3-bit binary: 7→111, 4→100, 3→011, 2→010. Combining these gives 111100011010.

Binary 10000000 has a single 1 in the 2^7 position (128). All other positions are 0, so the decimal value is 128.

Group binary digits into sets of 4 from right to left: 0001 1011 0011 1111. Convert each group to hex: 0001→1, 1011→B, 0011→3, 1111→F, giving 1B3F.

Group binary digits into sets of 3 from right to left: 001 101. The left group has leading zeros. Convert: 001→1, 101→5, giving octal 15.

Group binary digits into sets of 3 from right to left: 011 111. Convert: 011→3, 111→7, giving octal 37.

Binary 1001 can be grouped as 1001. In hexadecimal (base-16), each group of 4 binary digits represents one hex digit. Here, 1001 equals 9 in hex.

Group binary 101101 into sets of 4 from right: 0010 1101. Add leading zeros to complete groups. Convert: 0010→2, 1101→13(D), giving 2D.

Binary 1111 represents 8+4+2+1=15 in decimal. In hexadecimal, the values 0-9 and A-F represent 0-15, so 15 is represented by F.

Convert decimal 74 to hexadecimal by repeatedly dividing by 16: 74÷16=4 remainder 10. In hex, 10 is represented as A. So 74 in decimal equals 4A in hexadecimal.

Binary 11001 equals 1×16 + 1×8 + 0×4 + 0×2 + 1×1 = 25. Multiply each binary digit by its position value (powers of 2 from right to left) and sum the results.

93 divided by 16 gives quotient 5 and remainder 13 (D in hex), so 93 = 5D in hexadecimal. Repeated division by the base (16) gives digits from remainders.