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Reading with cin

Input works the same way in reverse: std::cin is the standard input stream, and >> reads a value from it into a variable.

#include <iostream>
#include <string>

int main() {
    std::string city;
    int year;
    double temp;
    std::cin >> city >> year >> temp;
    std::cout << city << " in " << year << ": " << temp << " degrees\n";
}

Oslo 2024
-3.5

Oslo in 2024: -3.5 degrees

Compared with scanf

• No &: >> takes its argument by reference (you'll learn references in the next module), so it can fill the variable directly.
• No format specifiers: the variable's type decides how the text is parsed. Reading into an int parses a number; reading into a std::string reads a word.
• Like scanf, >> skips whitespace before each value, so values can be separated by spaces or newlines.

std::string

std::string (from <string>) is C++'s real string type. It grows automatically as needed, knows its own length, and frees its memory when it's no longer used. No fixed-size arrays, no '\0' bookkeeping, and no buffer overflows when a user types a long name. Reading into it with >> reads one word (up to the next whitespace).

If a read fails (say, letters where an int was expected), the stream goes into a fail state and further reads do nothing. if (std::cin >> x) checks whether a read worked, like checking scanf's return value.

Your turn: read a name and a number of kills and print NAME got N kills.

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