Print Statements

Printing is one of the simplest debugging tools you have. Use it to check values, verify execution order, and confirm a branch actually runs.

If you are new to where code runs in a PROS project, review Basic C++ Syntax. Your print statements will usually live inside functions like initialize(), autonomous(), or opcontrol().

Using std::cout

std::cout is the standard C++ output stream. It comes from #include <iostream>. For technical details visit here.

#include "main.h"#include <iostream>void main(){  std::cout << "Driver started at " << pros::micros() << " microseconds" << std::endl;  return 0;}

What each part does

• std:: means the name comes from the C++ standard library namespace.
• cout means character output stream.
• << inserts data into the stream (conceptually a data link between robot and your computer).
• "Driver started at " is a string that gets combined with following statements.
• pros::micros() returns the current time in microseconds. This will output a number in the terminal.
• std::endl also makes a new line, but it flushes the stream too.

Notes

• std::cout works well when you want to chain values together.
• It can print built-in types like int, double, char, and strings.
• Custom types need their own output overload before std::cout can print them cleanly.
• "\n" adds a newline without flushing.

Using printf (C-style print)

printf is older than std::cout. It comes from #include <cstdio>. For technical details visit here.

#include "main.h"#include <cstdio>void main(){  int motor_port = 10;  double voltage = 12000.0;  char randomChar = 'H';  printf("Port: %d Voltage: %.0f randomChar: %c \n",         motor_port,         voltage,         randomChar);  return 0;}

Common format specifiers

• %d prints an integer.
• %f prints a floating-point number.
• %.xf prints a float with x digits after the decimal.
• %c prints a single character.
• %s prints a C-style string.
• %% prints a literal percent sign.

Notes

• printf is compact when you want tight control over formatting.
• The format specifier must match the variable type.
• Wrong specifiers can print garbage or cause bugs.
• This style is common in C code and older libraries.

Using std::print

std::print is the modern C++ formatting option. It uses {} placeholders instead of %d and %f. It comes from #include <print>. For technical details visit here.

#include <print>int main(){  int motor_port = 10;  double voltage = 12000.0;  std::print("Port: {} Voltage: {:.2f}\n",             motor_port,             voltage);               return 0;}

Why people like it

• The syntax is easier to read than printf.
• The placeholders match the argument order clearly.
• Formatting is more modern and safer than raw % specifiers.

Important note for PROS

std::print is a C++23 feature. Your current compiler must support C++23 and the <print> header.

If the compiler says <print> does not exist, your PROS toolchain is too old for std::print. Use std::cout or printf instead. To see prints open a integrated terminal and type pros terminal or pros t.

Note: I advise using pros mut to make (build), upload, and start a new brain terminal (where print statements will show up). Using pros mut will keep the radio on the download channel, meaning less drops while uploading and therefore faster! It also means undefined behavior might not show up, so make sure to test without uploading before going to a competition (I wasted a month of my life chasing this bug)!

Not an AD: Is printing too unprofessional for you? Do you want to add instructions on how to use v5gbd? Consider Contributing! This website won’t build itself!