Field (computer science)

Each field in a record has two components. One component is the field's datatype declaration. The other component is the field's identifier.

Memory fields

Fields may be stored in random access memory (RAM). The following Pascal record definition has three field identifiers: firstName, lastName, and age. The two name fields have a datatype of an array of character. The age field has a datatype of integer.

<span id="mwKw"></span><span class="k" id="mwLA">type</span><span class="w" id="mwLQ"> </span><span class="n" id="mwLg">PersonRecord</span><span class="w" id="mwLw"> </span><span class="o" id="mwMA">=</span> <span class="w" id="mwMQ"> </span><span class="k" id="mwMg">record</span> <span class="w" id="mwMw"> </span><span class="n" id="mwNA">lastName</span><span class="w" id="mwNQ"> </span><span class="o" id="mwNg">:</span><span class="w" id="mwNw"> </span><span class="k" id="mwOA">array</span><span class="w" id="mwOQ"> </span><span class="p" id="mwOg">[</span><span class="w" id="mwOw"> </span><span class="mi" id="mwPA">1</span><span class="w" id="mwPQ"> </span><span class="o" id="mwPg">..</span><span class="w" id="mwPw"> </span><span class="mi" id="mwQA">20</span><span class="w" id="mwQQ"> </span><span class="p" id="mwQg">]</span><span class="w" id="mwQw"> </span><span class="k" id="mwRA">of</span><span class="w" id="mwRQ"> </span><span class="kt" id="mwRg">Char</span><span class="o" id="mwRw">;</span> <span class="w" id="mwSA"> </span><span class="n" id="mwSQ">firstName</span><span class="w" id="mwSg"> </span><span class="o" id="mwSw">:</span><span class="w" id="mwTA"> </span><span class="k" id="mwTQ">array</span><span class="w" id="mwTg"> </span><span class="p" id="mwTw">[</span><span class="w" id="mwUA"> </span><span class="mi" id="mwUQ">1</span><span class="w" id="mwUg"> </span><span class="o" id="mwUw">..</span><span class="w" id="mwVA"> </span><span class="mi" id="mwVQ">20</span><span class="w" id="mwVg"> </span><span class="p" id="mwVw">]</span><span class="w" id="mwWA"> </span><span class="k" id="mwWQ">of</span><span class="w" id="mwWg"> </span><span class="kt" id="mwWw">Char</span><span class="o" id="mwXA">;</span> <span class="w" id="mwXQ"> </span><span class="n" id="mwXg">age</span><span class="w" id="mwXw"> </span><span class="o" id="mwYA">:</span><span class="w" id="mwYQ"> </span><span class="kt" id="mwYg">Integer</span> <span class="w" id="mwYw"> </span><span class="k" id="mwZA">end</span><span class="o" id="mwZQ">;</span>

In Pascal, the identifier component precedes a colon, and the datatype component follows the colon. Once a record is defined, variables of the record can be allocated. Once the memory of the record is allocated, a field can be accessed like a variable by using the dot notation.

<span id="mwaw"></span><span class="k" id="mwbA">var</span><span class="w" id="mwbQ"> </span><span class="n" id="mwbg">alice</span><span class="w" id="mwbw"> </span><span class="o" id="mwcA">:</span><span class="w" id="mwcQ"> </span><span class="n" id="mwcg">PersonRecord</span><span class="o" id="mwcw">;</span> <span class="n" id="mwdA">alice</span><span class="o" id="mwdQ">.</span><span class="n" id="mwdg">firstName</span><span class="w" id="mwdw"> </span><span class="o" id="mweA">:=</span><span class="w" id="mweQ"> </span><span class="s" id="mweg">'Alice'</span><span class="o" id="mwew">;</span>

Over time, the term field has been replaced with the terms data member and attribute. The following Java class has three attributes: firstName, lastName, and age.

<span id="mwjA"></span><span class="kd" id="mwjQ">public</span><span class="w" id="mwjg"> </span><span class="kd" id="mwjw">class</span> <span class="nc" id="mwkA">PersonRecord</span> <span class="p" id="mwkQ">{</span> <span class="w" id="mwkg"> </span><span class="kd" id="mwkw">private</span><span class="w" id="mwlA"> </span><span class="n" id="mwlQ">String</span><span class="w" id="mwlg"> </span><span class="n" id="mwlw">firstName</span><span class="p" id="mwmA">;</span> <span class="w" id="mwmQ"> </span><span class="kd" id="mwmg">private</span><span class="w" id="mwmw"> </span><span class="n" id="mwnA">String</span><span class="w" id="mwnQ"> </span><span class="n" id="mwng">lastName</span><span class="p" id="mwnw">;</span> <span class="w" id="mwoA"> </span><span class="kd" id="mwoQ">private</span><span class="w" id="mwog"> </span><span class="kt" id="mwow">int</span><span class="w" id="mwpA"> </span><span class="n" id="mwpQ">age</span><span class="p" id="mwpg">;</span> <span class="p" id="mwpw">}</span>