Technical Quick Recall
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tags: - cocubes - technical - cheat-sheet

Technical Quick Recall

Read this twice daily.

Data structures and algorithms

  • FIFO = queue; LIFO = stack.
  • BFS uses queue; shortest path in unweighted graph.
  • DFS uses stack/recursion.
  • Binary search requires sorted data.
  • BST inorder traversal is sorted.
  • Hash table average lookup O(1), worst O(n).
  • Merge sort O(n log n), stable, extra O(n).
  • Quicksort average O(n log n), worst O(nĀ²).
  • Heap root is min/max; build heap O(n).
  • Dijkstra does not allow negative edges.

Operating systems

  • Process has own address space; threads share process memory.
  • Page fault = required page absent from RAM.
  • Deadlock conditions: mutual exclusion, hold-and-wait, no preemption, circular wait.
  • Round Robin uses time quantum.
  • Aging prevents priority-scheduling starvation.
  • Paging fixed-size; segmentation variable-size.

Networking

  • Routing/IP = network layer; ports/TCP/UDP = transport layer; MAC/switch = data link.
  • TCP reliable/ordered; UDP low-overhead/connectionless.
  • DNS 53; HTTP 80; HTTPS 443; SSH 22; DHCP 67/68.
  • ARP IP ā†’ MAC; DNS name ā†’ IP; DHCP gives IP configuration.
  • /27 = 32 addresses, 30 traditional usable hosts.

Embedded

  • Microcontroller integrates CPU, memory and I/O.
  • ADC analog ā†’ digital; DAC digital ā†’ analog.
  • Interrupt reacts to event; polling repeatedly checks.
  • Watchdog protects from software hang.
  • UART async; SPI synchronous/full duplex; I2C two-wire/addressed.
  • Hard real-time deadline miss can be critical.

SDLC and QA

  • Waterfall sequential; Agile iterative; DevOps integrates development and operations.
  • Verification = product right; validation = right product.
  • Unit ā†’ integration ā†’ system ā†’ acceptance.
  • Regression checks old functions after change; retesting confirms a specific fix.
  • Black-box: BVA/equivalence/decision table; white-box: statement/branch coverage.

[[09_Revision/Last_Hour_Cheat_Sheet|Last-hour cheat sheet]]