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Function Signature

function fifo(llegada, cpu)

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Description

Implements the FIFO (First In First Out) scheduling algorithm, also known as FCFS (First Come First Served). Processes are executed in the order they arrive, forming a queue where the first process to arrive is the first to be executed. Each process runs to completion before the next one starts.

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Parameters

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llegada
number[]
required
Array of arrival times for each process. Each element represents when a process arrives in the system.
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cpu
number[]
required
Array of CPU burst times for each process. Each element represents how long a process needs to execute.

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Return Value

Returns an object containing scheduling metrics:
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inicio
number[]
Array of start times for each process (indexed by process ID).
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finalizacion
number[]
Array of completion times for each process (indexed by process ID).
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espera
number[]
Array of waiting times for each process. Calculated as: start_time - arrival_time.
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retorno
number[]
Array of turnaround times for each process. Calculated as: completion_time - arrival_time. Represents total time from arrival to completion.
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tiempoTotal
number
Total time required to complete all processes (maximum completion time).

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Example Usage

// Process arrival times
const llegada = [0, 1, 2, 3];

// CPU burst times
const cpu = [5, 3, 8, 6];

// Execute FIFO algorithm
const resultado = fifo(llegada, cpu);

console.log('Start times:', resultado.inicio);
console.log('Completion times:', resultado.finalizacion);
console.log('Waiting times:', resultado.espera);
console.log('Turnaround times:', resultado.retorno);
console.log('Total time:', resultado.tiempoTotal);

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Sample Output

{
  inicio: [0, 5, 8, 16],
  finalizacion: [5, 8, 16, 22],
  espera: [0, 4, 6, 13],
  retorno: [5, 7, 14, 19],
  tiempoTotal: 22
}

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Output Explanation

  • Process 0: Arrives at 0, starts at 0, runs for 5 units, completes at 5
  • Process 1: Arrives at 1, waits until 5, starts at 5, runs for 3 units, completes at 8
  • Process 2: Arrives at 2, waits until 8, starts at 8, runs for 8 units, completes at 16
  • Process 3: Arrives at 3, waits until 16, starts at 16, runs for 6 units, completes at 22

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Algorithm Details

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How It Works

  1. Processes are sorted by arrival time
  2. CPU executes processes in order of arrival
  3. If CPU is idle when a process arrives, it starts immediately
  4. Otherwise, the process waits for the current process to complete
  5. Each process runs to completion without interruption

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Complexity

  • Time Complexity: O(n log n) due to sorting by arrival time
  • Space Complexity: O(n) for storing process data and results

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Characteristics

  • Non-preemptive: Once a process starts, it runs to completion
  • Simple: Easy to understand and implement
  • Fair: Processes are served in arrival order
  • Convoy Effect: Short processes may wait for long processes ahead in queue

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