Editing Printf (section)

===1960s: BCPL and ALGOL 68===

<!-- Question: did the BCPL writef library routine already appear in 1967... or only later? -->
In 1967, [[BCPL]] appeared.<ref>{{cite web|url=http://www.cl.cam.ac.uk/users/mr/BCPL.html|title=BCPL|website=cl.cam.ac.uk|access-date=19 March 2018}}</ref> Its library included the {{code|writef}} routine.<ref>{{cite book |last1=Richards |first1=Martin |last2=Whitby-Strevens |first2=Colin |title=BCPL - the language and its compiler |date=1979 |publisher=Cambridge University Press |page=[https://archive.org/details/richards1979bcpl/page/n57 50] |url=https://archive.org/details/richards1979bcpl}}</ref> An example application looks like this:
<syntaxhighlight lang="text">
WRITEF("%I2-QUEENS PROBLEM HAS %I5 SOLUTIONS*N", NUMQUEENS, COUNT)
</syntaxhighlight>

Hereby:

* {{code|%I2}} indicates an [[Integer (computer science)|integer]] of width 2 (the order of the format specification's field width and type is reversed compared to C's {{code|printf}});
* {{code|%I5}} indicates an integer of width 5;
* {{code|*N}} is a BCPL ''language'' [[escape sequence]] representing a [[newline]] character (for which C uses the escape sequence {{code|\n}}).

In 1968, [[ALGOL 68]] had a more function-like [[API]], but still used special syntax (the {{code|$}} delimiters surround special formatting syntax):
<syntaxhighlight lang="cpp">
printf(($"Color "g", number1 "6d,", number2 "4zd,", hex "16r2d,", float "-d.2d,", unsigned value"-3d"."l$,
         "red", 123456, 89, BIN 255, 3.14, 250));
</syntaxhighlight>

In contrast to Fortran, using normal function calls and data types simplifies the language and compiler, and allows the implementation of the input/output to be written in the same language.

These advantages were thought to outweigh the disadvantages (such as a complete lack of [[type safety]] in many instances) up until the 2000s, and in most newer languages of that era I/O is not part of the syntax.

People have since learned<ref>{{cite web|url=https://owasp.org/www-community/attacks/Format_string_attack |title = Format String Attack}}</ref> that this potentially results in consequences, ranging from security exploits to hardware failures (e.g., phone's networking capabilities being permanently disabled after trying to connect to an access point named "%p%s%s%s%s%n"<ref>{{cite web|url=https://www.bleepingcomputer.com/news/security/iphone-bug-breaks-wifi-when-you-join-hotspot-with-unusual-name/|title = iPhone Bug Breaks WiFi When You Join Hotspot With Unusual Name}}</ref>). Modern languages, such as [[C++20]] and later, tend to include format specifications as a part of the language syntax,<ref>{{cite web|url=https://en.cppreference.com/w/cpp/utility/format/spec|title=C++20 Standard format specification}}</ref> which restore type safety in formatting to an extent, and allow the compiler to detect some invalid combinations of format specifiers and data types at compile time.