Microsoft KB Archive/160740

= How to use the vector::size, vector::capacity, and vector::push_back STL functions in Visual C++ =

Article ID: 160740

Article Last Modified on 7/15/2005

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APPLIES TO

 The Standard C++ Library, when used with:  Microsoft Visual C++ 4.2 Enterprise Edition

 Microsoft Visual C++ 5.0 Enterprise Edition

 Microsoft Visual C++ 6.0 Enterprise Edition

 Microsoft Visual C++ 4.2 Professional Edition</li></ul>

 Microsoft Visual C++ 5.0 Professional Edition</li></ul>

 Microsoft Visual C++ 6.0 Professional Edition</li></ul>

 Microsoft Visual C++ 6.0 Standard Edition</li></ul>

 Microsoft Visual C++ .NET 2002 Standard Edition</li></ul> </li> Microsoft Visual C++ .NET 2003 Standard Edition</li></ul>

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This article was previously published under Q160740

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Note Microsoft Visual C++ NET (2002) supported both the managed code model that is provided by the .NET Framework and the unmanaged native Windows code model. The information in this article applies to unmanaged Visual C++ code only.

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SUMMARY
The sample code below illustrates how to use the vector::size, vector::capacity, and vector::push_back functions.

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Prototypes
size_type vector::capacity const size_type vector::size const void vector::push_back(const _TYPE& _X) Note The class/parameter names in the prototype may not match the version in the header file. Some have been modified to improve readability.

Description

 * The sample declares an empty vector of integers.
 * It outputs the size and capacity of the vector.
 * It adds a single element to the vector, then outputs the size and capacity again.

Sample code
////////////////////////////////////////////////////////////////////// // // Compile options needed: /GX // // Capacity.cpp - Illustrates vector::capacity and vector::size // // Functions: // //   vector::capacity  - Return # of elements for which memory has //                       been allocated. // //   vector::size      - Return # of elements in the vector // //   vector::push_back - Append (insert) an element to the end of a //                        vector, allocating memory for it if necessary. // // Written by Tom Campbell // of Microsoft Corporation // Copyright (c) 1996 Microsoft Corporation. All rights reserved. //////////////////////////////////////////////////////////////////////

// The debugger can't handle symbols more than 255 characters long. // STL often creates symbols longer than that. // This disables the warning issued when symbols are longer than 255 chars.
 * 1) pragma warning(disable:4786)


 * 1) include
 * 2) include

using namespace std; // std c++ libs implemented in std #endif
 * 1) if _MSC_VER > 1020  // if VC++ version is > 4.2

typedef vector<int, allocator > INTVECTOR;

void main {   // Dynamically allocated vector begins with 0 elements. INTVECTOR theVector;

// Show size (current # of elements) and capacity (# of elements   // there's room for) of the empty vector. cout << endl << "Vector with no elements:" << endl; cout << "theVector's size is: " << theVector.size << endl; cout << "theVector's capacity is: " << theVector.capacity << endl;

// Add one element to the end of the vector, an int with the value 42. // Allocate memory if necessary. theVector.push_back(42) ;

// Show size & capacity after adding an element to the vector. cout << endl << "After adding 1 element:" << endl; cout << "theVector's size is: " << theVector.size << endl; cout << "theVector's capacity is: " << theVector.capacity << endl; }

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