What does this Operating Systems cheat sheet cover?

It has 10 sections: Processes, Scheduling, Threads, Synchronization, Deadlock, Memory, Paging, Virtual Memory, File Systems and I/O and Syscalls. Together they cover the topics a typical Operating Systems exam tests, including processes and threads, CPU scheduling algorithms, synchronization: locks, semaphores and deadlock conditions and avoidance.

Is the operating systems cheat sheet free?

The first part is free to read on this page, with no account needed. The full sheet opens in the app with Unlimited ($4.99 a month or $19 for a semester), where you can edit it, print it or save it as a PDF. It is one US Letter page and prints cleanly in black and white or colour.

Can I bring this Operating Systems cheat sheet to my exam?

Only if your course allows a note sheet, so check the syllabus. This one is a single US Letter page. If your exam allows a different size, such as a 3x5 or 4x6 index card or one page front and back, Cheat Sheet AI makes one at exactly that size from your own lecture notes.

The sheet was written by our engine from a standard course outline, then a second model fact-checked every formula and statement against it; it corrected 5 statements before publishing. Notation and emphasis vary between courses, so check it against your own lecture notes.

Can I make a Operating Systems sheet from my own notes?

Yes. Upload your lecture slides, notes or study guide and Cheat Sheet AI writes a sheet in your course's notation, sized to exactly the space your exam allows. Your first sheets are free.

ComputingOperating Systems

Operating Systems Cheat Sheet — 1-page PDF

Processes, scheduling, synchronization, memory, files, I/O, syscalls. The whole course on one dense, printable page for your midterm or final, with every formula typeset and worked examples where they help.

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For a specific exam: Operating Systems Final exam study sheet.

1 pageUS Letter
10 sections9 topics
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Preview of the one-page Operating Systems cheat sheet: Processes, scheduling, synchronization, memory, files, I/O, syscalls — the whole course, one page

On the sheet

What’s on it

The topics a typical Operating Systems exam tests, all on the one page.

Processes and threads
CPU scheduling algorithms
Synchronization: locks, semaphores
Deadlock conditions and avoidance
Memory management and paging
Virtual memory and page replacement
File systems
I/O and disks
System calls

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The free part, as text

The free part of the sheet, section by section. Unlock the full sheet to read the rest, edit any block, and print it or save it as a PDF.

01Processes

process: Program in execution; has PID, address space, CPU state, open files.
thread: Execution unit inside a process; shares code/data/files, has own PC, regs, stack.
PCB: Process Control Block: PID, state, PC, regs, scheduling info, memory info, I/O status.

Process states

State	Meaning
new	created
ready	waiting for CPU
running	on CPU
blocked	waiting for event/I/O
terminated	finished

Throughput

throughput = \frac{# jobs completed}{unit time}

Scheduler/performance metric.

Turnaround

T_{t u r n} = T_{co m pl e t i o n} - T_{a r r i v a l}

Per process.

Waiting

T_{w ai t} = T_{t u r n} - T_{C P U} - T_{I / O}

If total CPU burst time known; often $T_{w ai t} = T_{t u r n} - service time$ .

Watch out:Context switch overhead: scheduler choice affects real CPU time; ignore only if problem states so.

02Scheduling

preemptive: CPU can be taken away before burst ends.

03Threads

kernel-level thread: Managed by OS; blocking isolated per thread; higher overhead.

Multithreading models

Model	Meaning
many-to-one	many user threads $\to$ one kernel thread
one-to-one	each user thread maps to kernel thread
many-to-many	many user threads multiplex on many kernel threads

Speedup

S = \frac{T _{serial}}{T _{parallel}}

Idealized parallel gain from threads.

Watch out:Shared address space => races unless synchronization used; thread-safe code needed for shared data.

race condition: Output depends on relative timing of concurrent accesses.

04Synchronization

critical section: Code segment accessing shared data/resources.
mutual exclusion: At most one thread/process in critical section at a time.
lock: Binary synchronization object; acquire/release.

Semaphore

S \in Z

Integer synchronization variable.

05Deadlock

Prevention: break one of 4 conditions (e.g. request all at once to kill hold-and-wait).
Avoidance: only grant requests that keep state safe (Banker).
Detection/recovery: allow deadlock, then detect cycle and recover.
Ignore: if rare/costly to handle.

Watch out:Circular wait prevention: impose total order on resource types; acquire in increasing order only.

06Memory

address space: Set of virtual addresses a process can use.
logical address: CPU-generated address; translated to physical address.
MMU: Memory Management Unit: hardware translating virtual to physical addresses.
paging: Split virtual memory into fixed-size pages and physical memory into frames.

Address split

virtual address = ⟨ p, d ⟩

page number $p$ , offset $d$ .

Translation

physical address = ⟨ f, d ⟩

frame number $f$ from page table; same offset $d$ .

page table: Maps page number $p$ to frame number $f$ plus valid/protection bits.
TLB: Translation Lookaside Buffer: cache of recent page-table entries.

Effective access time

E A T = h (t_{T L B} + t_{m}) + (1 - h) (t_{T L B} + 2 t_{m})

If TLB hit ratio $h$ and memory access time $t_{m}$ .

07Virtual Memory

Page-fault rate

fault rate = \frac{# faults}{# memory references}

Used to tune replacement / working set.

local replacement: Victim chosen from same process's frames.
global replacement: Victim chosen from all frames in system.

Watch out:Too few frames => high fault rate; adding CPU processes can worsen throughput via thrashing.

08File Systems

file: Named collection of data blocks with metadata.
inode: Metadata record: size, owner, permissions, block pointers.
directory: Mapping from file name to inode / file control info.

Allocation

Method	Pros	Cons
contiguous	fast sequential	external fragmentation
linked	no external fragmentation	slow random access
indexed	good random access	index overhead

free-space bitmap: 1 bit per block; bit value indicates free/used.

File links

hard link $\Rightarrow$ same inode $;$ symbolic link $\Rightarrow$ pathname reference

Hard links usually not across file systems.

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Also on the full Operating Systems sheet

8 more sections, with every definition, formula and worked example. Unlimited unlocks every full sheet in the library to edit, print or save as a PDF, and makes unlimited sheets from your own notes.

Scheduling

nonpreemptive
Common schedulers
RR response
aging

Threads

user-level thread

Synchronization

wait signal
binary semaphore
counting semaphore
Classic problems

Deadlock

deadlock
4 necessary conditions
safe state
Banker safety

Paging

page fault
dirty bit
valid bit
Replacement
Belady

Virtual Memory

demand paging
working set
thrashing

File Systems

buffer cache

I/O and Syscalls

blocking I/O
nonblocking I/O
DMA
interrupt
Disk scheduling
Disk seek
system call
Common syscalls

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FAQ

Questions

About the Operating Systems sheet and making your own.

What does this Operating Systems cheat sheet cover?: It has 10 sections: Processes, Scheduling, Threads, Synchronization, Deadlock, Memory, Paging, Virtual Memory, File Systems and I/O and Syscalls. Together they cover the topics a typical Operating Systems exam tests, including processes and threads, CPU scheduling algorithms, synchronization: locks, semaphores and deadlock conditions and avoidance.
Is the operating systems cheat sheet free?: The first part is free to read on this page, with no account needed. The full sheet opens in the app with Unlimited ($4.99 a month or $19 for a semester), where you can edit it, print it or save it as a PDF. It is one US Letter page and prints cleanly in black and white or colour.
Can I bring this Operating Systems cheat sheet to my exam?: Only if your course allows a note sheet, so check the syllabus. This one is a single US Letter page. If your exam allows a different size, such as a 3x5 or 4x6 index card or one page front and back, Cheat Sheet AI makes one at exactly that size from your own lecture notes.
How accurate is it?: The sheet was written by our engine from a standard course outline, then a second model fact-checked every formula and statement against it; it corrected 5 statements before publishing. Notation and emphasis vary between courses, so check it against your own lecture notes.
Can I make a Operating Systems sheet from my own notes?: Yes. Upload your lecture slides, notes or study guide and Cheat Sheet AI writes a sheet in your course's notation, sized to exactly the space your exam allows. Your first sheets are free.

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